Some questions about micro SD - General Accessories

Hi guys, I have a few questions about micro SD:
1) Does higher class drain more battery?
2) I just purchased a LG optimus 2x, is a class 6 enough for me? or do I need to go all the way to class 10?
3) Will higher class cause lagness to the phone?
Thanks guys

akira de aimbuster said:
Hi guys, I have a few questions about micro SD:
1) Does higher class drain more battery?
2) I just purchased a LG optimus 2x, is a class 6 enough for me? or do I need to go all the way to class 10?
3) Will higher class cause lagness to the phone?
Thanks guys
Click to expand...
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1. From what I've seen, it seems some higher class cards drain battery more... I think the brand and quality of chips make more difference with battery, though.
2. Is class 6 enough for what? What are you using the card for? If it's strictly for taking pictures or videos, or transferring large files, or other tasks that you only need sequential write and reading, then higher class would be quicker for that. But class 6 is pretty quick with sequential reading/writing... it's up to you if you need higher. What are you using the card for?
3. Yes, higher class cards can cause lagness if you have apps or OS files on it, or if the phone is trying to access many different parts of the card quickly. Generally, for using with a phone, you will get better performance with class 2 or 4 cards. Higher class cards generally have slower access times and slower random access speed and random read and write speeds. Class 6 and 10 are better for digital cameras, or for transferring large files, but for use with a phone, where you may run apps off it or have the OS trying to access many bits of data from different parts of card, class 2 or 4 usually perform better there.

zarathustrax said:
...Yes, higher class cards can cause lagness if you have apps or OS files on it, or if the phone is trying to access many different parts of the card quickly. Generally, for using with a phone, you will get better performance with class 2 or 4 cards. Higher class cards generally have slower access times and slower random access speed and random read and write speeds. Class 6 and 10 are better for digital cameras, or for transferring large files, but for use with a phone, where you may run apps off it or have the OS trying to access many bits of data from different parts of card, class 2 or 4 usually perform better there.
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Can it be true; I suspect the "slower access times and slower random access speed and random read and write speeds" coming from higher class (10) microsd cards have to do also with bad quality, cheap (see chinese) chips that hit the market with the class 10 hoax. I hope "serious" manufacturers will produce cards that could achieve not only sequential, but also satisfactory random speeds.

Are there any sites that rank microSD cards based on random access time?
THG has some data for miniSD cards but most other sites have scattered reviews and no direct ranking.

me00016 said:
Can it be true; I suspect the "slower access times and slower random access speed and random read and write speeds" coming from higher class (10) microsd cards have to do also with bad quality, cheap (see chinese) chips that hit the market with the class 10 hoax. I hope "serious" manufacturers will produce cards that could achieve not only sequential, but also satisfactory random speeds.
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Click to collapse
Well there are quality cards that do good at both... a Sandisk class 4 is one of the best all around I've seen. It pretty much gets class 6 sequential write speeds, and still has great access time and random speeds.
But the lag cause by class 10's and 6 isn't only because of low quality... it's caused because the higher class chips are designed to initialize the part of the card it's about to use, which gives much better sequential speeds, but hurts the access time and random read and write where many parts of the chip are accessed quickly getting small bits of info in many different parts. In this case, the initialization that the chip is doing causes it to take much longer, as it still initializes each part before accessing it. That extra step it's doing adds up to a lot of extra time when its using lots of random parts of the chip to read or write only a small bit of data.
Cards that don't do this initialization and just begin accessing immediately is obviously going to be quicker when using many different parts of card.

zarathustrax said:
2. Is class 6 enough for what? What are you using the card for? If it's strictly for taking pictures or videos, or transferring large files, or other tasks that you only need sequential write and reading, then higher class would be quicker for that. But class 6 is pretty quick with sequential reading/writing... it's up to you if you need higher. What are you using the card for?
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Most probably I will dump everything into the card, reading games from it, using gps with map files inside the sd...etc. So I guess a class 6 is sufficient. But now people are telling me even class 4 is sufficient, while some say that they observed huge different from class4 vs class 6, I got confused
May I know if android is using sequential access or random access? Or is it depends on the software?

akira de aimbuster said:
Most probably I will dump everything into the card, reading games from it, using gps with map files inside the sd...etc. So I guess a class 6 is sufficient. But now people are telling me even class 4 is sufficient, while some say that they observed huge different from class4 vs class 6, I got confused
May I know if android is using sequential access or random access? Or is it depends on the software?
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Click to collapse
I'm confused too, after 2 months trying to find the optimum 32gb microsd for my SGS. Well, the thing gets complicated (especially for 32gb capacities) because of many reasons:
- Inconsistent quality assurance-high percentage of defect cards, sometimes of the same lot, even from top brands. This could be not only a non working card, but also small but critical problems like write failure, freeze, etc.
- Users, we don't know what we want microsd for; surely we all want to upgrade the memory of our phones, but it seems that others don't like to wait long transfering 1080p movies in the device, others want to use app2sd with android. I've come to the conclusion that right now in the market there is not a product that can do all jobs satisfactory (maybe Sandisk c4?).
- Fake cards.

Related

better 32GB MicroSDHC than Sandisk

Anyone know of a better 32GB MicroSD card than the Sandisk? It's only class 2, but its random write performance is leaps and bounds better than both the Kingston and the Patriot LX, which helps to prevent severe lag when using apps2sdext.
I had hope a class 10 Patriot would at least be as good, but the results couldn't have been more different. Ideally I would like more sequential write speed without having to sacrifice random write performance.
We have been using/ Distributing microSD Class 10 cards from Wintec. I am using there 16 GB Class 10 on a Samsung Captivate. If you could direct me to a Android test program you like, I would be glad to run it. I have had no problems since switching.
but sandisk is the best around! for the price.....
nokia or kingstone but i prefer sandisk for the price
i have a sandisk and the card is great
I have never found anything better or more reliable than Sandisk. No bells and whistles just solid performance.
i need this type of card
but with model to choose
The OCZ branded cards are good in my experience.
Lexar's apparently got some top-notch class-10 32giggers out...
You can order them straight from their website (they might be a little backlogged though).
Class 2 and 4 cards have better random access speed and random read/write than class 6 or 10 cards in general. To get higher sequential write speeds, manufacturers sacrifice the random access speeds. That's just how it is.
The best all around card I've ever found is Sandisk class 4.
My 32gb Sandisk class 4 outperforms any other class 10 or 2 32gb card I've tested in the random access and random read/write speeds. That's what's most important when using with WP7 or Android when using it for apps or OS files that need to be accessed quickly. Class 6 and 10 cards are setup to initialize the area of the card that is about to be used to make the sequential write/read quicker, but it takes extra time in the beginning to do the initialization. If your using the card where you need to access small bits of info from various parts of card quickly, you will do best with class 2 or 4.
Most people seem to assume that the higher the class, the better the card is for everything, but that's not how it is. Different purposes need different kinds of speed... cards with higher sequential speeds have lower random speeds.
zarathustrax...it seems to be a hot topic. after all, repetition is the best way to learn
Will Scripts Improve random access speeds?
zarathustrax said:
Class 2 and 4 cards have better random access speed and random read/write than class 6 or 10 cards in general. To get higher sequential write speeds, manufacturers sacrifice the random access speeds. That's just how it is.
The best all around card I've ever found is Sandisk class 4.
My 32gb Sandisk class 4 outperforms any other class 10 or 2 32gb card I've tested in the random access and random read/write speeds. That's what's most important when using with WP7 or Android when using it for apps or OS files that need to be accessed quickly. Class 6 and 10 cards are setup to initialize the area of the card that is about to be used to make the sequential write/read quicker, but it takes extra time in the beginning to do the initialization. If your using the card where you need to access small bits of info from various parts of card quickly, you will do best with class 2 or 4.
Most people seem to assume that the higher the class, the better the card is for everything, but that's not how it is. Different purposes need different kinds of speed... cards with higher sequential speeds have lower random speeds.
Click to expand...
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Noob question: recently, scripts have been produced to, for example, speed the reading of photos in the gallery. Will those same scripts improve the class 10 cards such that their performance is better than class 4 cards?
Ashyford said:
Noob question: recently, scripts have been produced to, for example, speed the reading of photos in the gallery. Will those same scripts improve the class 10 cards such that their performance is better than class 4 cards?
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Click to collapse
They may improve speeds a little in your phone, but it doesn't change how the sd cards controller acts. So no, it won't make class 10 have better random speeds and access times than a high quality class 2 or 4. The controller in the SD card and the actual NAND memory chip itself decides how the card reads and writes and the speeds it has.
andisk is the best
i want to know too . . . .

What speed and/or Class card do you use for your memory card?

Hey
Im sorta "hell bent" on getting a 32GB microSD Class 10 card ( http://forum.xda-developers.com/showthread.php?t=1031312 ) but they are very limited to find. I want a Class 10 because of data transfer and the snapping of pictures/video taking is alot quicker.
I just want to know what class did you get, for what purpose, and what do you use your mobile device most (taking pictures, internet, calling, etc).
Just so everyone knows (just in case):
The Speed Class Rating is the official unit of speed measurement for SD Cards, defined by the SD Association. The Class number represents a multiple of 8 Mbits/s (1 MB/s), and meets the least sustained write speeds for a card in a fragmented state.
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Hey,
I was really keen on getting a class 10 32Gb too, but they are very expensive. In then end I opted for a 16Gb class 10 as Play.com had them on offer a month or so ago. I got a sandisk one. Just had a look for a link, but I don't think they have them now.
Guess you could get it anywhere though. I paid £15 including delivery.
I've done a couple of measurements and it's definitely performing at class 10 speeds. I have an HD2 running an Android Gingerbread SD build and the speed has been more than adequate.
My use is mostly internet, texts and calls. I have done some video/photo stuff since getting the card and it's definitely fast enough.
I used to have a class 6 PNY 8Gb one in there and it's a hell of an improvement, especially now I'm on an SD build. The only thing I would say is android takes a fair while to do it's 'preparing SD card' business when I turn the phone on, but no other issues to report. the new card seems to have helped with the hang issues on installing market apps too, which is nice.
Also - did a defrag on it with Mydefrag (beautiful tool!), which seems to have helped too.
Hope that helps!
I still use my stock 8GB card I got with my phone. My main use is pictures and apps. Its a class 2.
Sent from my HTC Inspire 4G
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I'm currently using 2 32GB Sandisk cards... one is marked class 2, one is marked class 4, but both their average write speeds are pretty similar. They could accurately be marked as class 6.
But really, the class is not important to me. When it comes to choosing a card to use in my phone, I look for cards with quick access times and fast random read and write speeds. Class ratings are really only important when the cards are going to be used in a digital camera or be used as a flash storage drive where you will be transferring large files back and forth.
When it comes to cell phones, a card that can quickly access files and can read/write to many different parts of the card quickly is much more important than a card that can write sequentially fast. You may be able to take large pictures with the camera more quickly with a higher class card, but many cards sacrifice their random access speeds to get that high sequential write speed. This can cause lags and performance loss when running apps or system files off the higher class cards.
The best cards to generally use in cell phones is a class 2 or 4. Many class 6 may perform well, too. There may even be class 10 cards that don't sacrifice that random access speeds. Quality and brand are generally much more important than class to get good access speeds and random read/write speeds.
I really think there needs to be a new rating system for access speeds and random speeds. In general, the lower class cards have better random access speeds, but that's not always the case. There are plenty of class 2 and 4 cards that have terrible random access times, and many class 6 and even 10 that still have great random access. Unfortunately, there's no way to know how a card rates in these areas until you actually test it.
I've always had good results from Sandisk cards... and terrible results from Kingston.
Hopefully, since WP7 requires cards used with it to have good random access speeds, we might start seeing some lines of microSD cards that rate these speeds.
But for now, if you're using the card with wp7, or running android off the card, or running apps or other system files off the card, you will generally have better results with high-quality lower-class cards. I have only been using Class 2 and 4 Sandisk recently. Hopefully a new class and rating system is created for using these cards with smartphones. We are using them more and more for the purpose of internal phone memory... especially windows phone 7, and even with android you see more people making partitions on their cards to use as internal memory to run app and system files. We need a better rating system for cards, cause the current class rating is pretty much meaningless for smartphone purposes.
homescrub said:
I still use my stock 8GB card I got with my phone. My main use is pictures and apps. Its a class 2.
Sent from my HTC Inspire 4G
XDA Developers Premium App
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Thanks but vote
Seiphr said:
Also - did a defrag on it with Mydefrag (beautiful tool!), which seems to have helped too.
Click to expand...
Click to collapse
Defraging a flash based storage device does nothing and actually makes its lifetime smaller.
zarathustrax said:
I'm currently using 2 32GB Sandisk cards... one is marked class 2, one is marked class 4, but both their average write speeds are pretty similar. They could accurately be marked as class 6.
But really, the class is not important to me. When it comes to choosing a card to use in my phone, I look for cards with quick access times and fast random read and write speeds. Class ratings are really only important when the cards are going to be used in a digital camera or be used as a flash storage drive where you will be transferring large files back and forth.
When it comes to cell phones, a card that can quickly access files and can read/write to many different parts of the card quickly is much more important than a card that can write sequentially fast. You may be able to take large pictures with the camera more quickly with a higher class card, but many cards sacrifice their random access speeds to get that high sequential write speed. This can cause lags and performance loss when running apps or system files off the higher class cards.
The best cards to generally use in cell phones is a class 2 or 4. Many class 6 may perform well, too. There may even be class 10 cards that don't sacrifice that random access speeds. Quality and brand are generally much more important than class to get good access speeds and random read/write speeds.
I really think there needs to be a new rating system for access speeds and random speeds. In general, the lower class cards have better random access speeds, but that's not always the case. There are plenty of class 2 and 4 cards that have terrible random access times, and many class 6 and even 10 that still have great random access. Unfortunately, there's no way to know how a card rates in these areas until you actually test it.
I've always had good results from Sandisk cards... and terrible results from Kingston.
Hopefully, since WP7 requires cards used with it to have good random access speeds, we might start seeing some lines of microSD cards that rate these speeds.
But for now, if you're using the card with wp7, or running android off the card, or running apps or other system files off the card, you will generally have better results with high-quality lower-class cards. I have only been using Class 2 and 4 Sandisk recently. Hopefully a new class and rating system is created for using these cards with smartphones. We are using them more and more for the purpose of internal phone memory... especially windows phone 7, and even with android you see more people making partitions on their cards to use as internal memory to run app and system files. We need a better rating system for cards, cause the current class rating is pretty much meaningless for smartphone purposes.
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Great post as in the other thread I may have to go with a Class 4 (as there are even less Class 6) card as it will also lower the price in my budget. Cant have everything...
I got a good deal on a Samsung 16 gb class 2, figured I'd go for it because I don't really use my phone for too much HD recording . However, it consistently benchmarks at class 6 speeds.
Yes, I did vote
32gb sandisk class 4
No clue, is there a program which can be used to check it in a SGS?
johan81 said:
No clue, is there a program which can be used to check it in a SGS?
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h2testw
Thanks
Thanks for all the votes
It seems since Im on a budget, Im going to have to go with a Class 4 even though it hurts as I (thought) a Class 10 was needed. I just hope I dont notice it when taking pictures.
SanDisk without a doubt right?
riahc3 said:
SanDisk without a doubt right?
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Im tempted to make a thread about this as well
I just like to make sure what I buy before I do it. Makes me more sure about what Im buying.
Thanks to everyone who has helped me in these 2 (well problably soon 3) threads. I appreciate it
riahc3 said:
Im tempted to make a thread about this as well
I just like to make sure what I buy before I do it. Makes me more sure about what Im buying.
Thanks to everyone who has helped me in these 2 (well problably soon 3) threads. I appreciate it
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Click to collapse
Definitely Sandisk....if getting 32GB, look for model # ending in B35A or B35N. I think that's the one I got. I'll double check tonight and let you know. It was listed as class 2 when I ordered it, but it was marked class 4 when I got it, and it had sequential write speeds equal to class 6 (6MB/Sec). I also have a 32GB with model # ending in A11M... this one was mark class 2, but I think newer ones are also marked class 4. Not sure if the newer ones marked class 4 have better performance than the ones marked class 2, but mine which is marked class 2 could also easily be marked class 6 and be as fast in sequential write speeds as most class 6 of other brands... but the class 2 A11M is not quite as fast as the class 4 B36A that I have in both sequential write/read and random read/write & access times. But like I said, the newer A11Ms marked as class 4 may have better performance than the ones marked class 2, and the performance difference between my 2 32GB Sandisks is not very big.... both are VERY good cards in overall performance.
I got both my cards from provantage, I believe.
zarathustrax said:
The best cards to generally use in cell phones is a class 2 or 4. Many class 6 may perform well, too. There may even be class 10 cards that don't sacrifice that random access speeds. Quality and brand are generally much more important than class to get good access speeds and random read/write speeds.
Click to expand...
Click to collapse
Hey zarathustrax, I'm maintaining a microSD benchmark results thread and we have quite a few results now, and it backs up everything you are saying. The 32GB Class2 Sandisk (when it was available) owns everything on random writes. Followed by the 32 Class4 Sandisk.
By comparison, a 32GB Class10 Lexar is benching 350 times slower for random writes than the Sandisk. And yet only offers a doubling of sequential write speed.
Additionally, I maintain an in-phone microSD benchmark thread too. But the results are pretty much cached out by whatever ROM you are running on your phone. So slow cards become much faster, and fast cards become much slower. In the end we found that all cards were performing at around the same speeds. Its only when you changed ROMs would you see a change in in-phone card speed.
Out of phone benchmark link...
http://forums.whirlpool.net.au/forum-replies.cfm?t=1582172
In-phone benchmark link...
http://forums.whirlpool.net.au/forum-replies.cfm?t=1468705
Thanks. Im going to read your links now and see if there are model numbers and get some cards (I should have already bought the card before yesterday)
Thanks again stumo5
Damn, no model numbers
Stores that are near me and deliver to me only offer Kingston lol...
Holy ****!
I have found one that has a Sandisk; The only problem is that on the webpage it says that it is a SDSDQM-032G-B35 but the picture shows a 2 written on the card, meaning Class 2. I pretty much refuse going from a Class 10 to a Class 2 and besides the price is 95....
Im going to call and get the model number anyhow....
Kingston 60 bucks
Sandisk 95 bucks
Man how they like to **** consumers in the ass Anyways, he said that what was shown to him was divided by categories and he couldnt tell me the exact model number as it just showed him prices and who supplied it but I rather pay on eBay a Lexar Class 10 at 96 rather than a Sandisk Class 2/4 at 95.
More comparisons: A Sandisk Class 2 32GB at 89 bucks on eBay.
I mean I really have to juggle and ask my self: Is it really worth it? Being on a slight budget, Im not sure.
stumo5 - Has anyone done tests in your microsd exam on TopRAM? I might get them at the end as the prices are just rapist ( ). zarathustrax, the price doesnt justify to me at the end, unless I will notice it.
My main dilema was how pictures were going to be taken as I imagine there will be a lag in picture when I press it and when it is actually taken. Also file transfers and installing/running applications from the SD card. Your explanation was great zarathustrax but Im not sure if its going to be worth the price.
My first smartphone (Nokia E70) I went with Kingston but it surprises me in a way that people talk so bad about Kingston in the flash memory card area.
And I now see on eBay a Sandisk 32GB Class 4 at about 75....More or less.
I'm currently using the 8gb one that came with my Desire Z although I have a class 6 8Gb somewhere that I bought but I haven't felt the need to swap yet for some reason I can't tell a difference

What Type Of MicroSDHC Class, Should I Buy For Arc?

Hey Ppl...
What Type Of MicroSDHC Class, Should I Buy For Arc?
Class 4, 6 or 10?
Right now i´ve Class 2
Its better to get the highest which is class 10 if u can afford..
The Classes guarantess a lowest speed while newely formated
class 2 is 2MB/s
class 6 is 6MB/s
class 10 is 10MB/s
and so on
but with luck a class 2 card can outpreform a class 6 card but you never know untill you have bought it.
the use of a higher class is more important how often you transfer big amout of files/data from and to your phone (this is when you will notice a slow card)
everyday use the class 2 card that is shipped with the phone works perfect
I'm going for a 16GB Kingston Class 10 for mine, might go 32GB but that'll depend on how much I get for my X10 on ebay.
XperienceD said:
I'm going for a 16GB Kingston Class 10 for mine, might go 32GB but that'll depend on how much I get for my X10 on ebay.
Click to expand...
Click to collapse
Put my X10 on ebay yesterday!
How much you asking for it?
For no OT, I bought a 32 GB Lexar class 10 MicroSDHC
LususNaturae said:
Put my X10 on ebay yesterday!
How much you asking for it?
Click to expand...
Click to collapse
Not sure yet, it's a bit weared so not expecting a great deal.
Here's the thing: the class of an SD card only defines how fast you can *write* to it. The read speeds of all cards tend to be the same regardless of class.
What a faster class of SD card will get you:
* faster copying of files from PC to SD, e.g. music, video
What it won't get you:
* a faster running phone (i.e. no 'snappier' performance)
* apps loading faster
* faster copying of files from SD to PC
* music/video playback improvements
* faster installation of apps - these are stored in internal memory, and even for builtin apps2sd the limiting factor tends to be the download speed
What it might get you:
* faster stills camera operation (havent checked for the arc, there may be bottlenecks elsewhere in the system, e.g. cpu)
* i thought it might solve the video capture glitching, but apparently the new firmware has fixed this regardless of SD card class.
* some apps which write a lot of data to SD card may run faster (note however that for most apps data is stored in internal storage)
Nothing inherently wrong with getting a faster card, just dont delude youself you'll see much of a difference in day-to-day operation.
Oh, i forgot, EXCEPT one other thing: If youre using 'full' apps2sd on a rooted phone (i.e. with an ext2 partition moving all apps+data+dalvik cache onto it) it will definitely help to have a faster class of SD card. Dunno if anyone really still does that these days...
I've always found going bigger and faster to be best, but valid points made.
daveybaby said:
Here's the thing: the class of an SD card only defines how fast you can *write* to it.
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Click to collapse
That's incorrect - the class rating is a guarantee of both read and write speeds.
daveybaby said:
The read speeds of all cards tend to be the same regardless of class.
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Click to collapse
You can't guarantee that any more than you can guarantee that a Class 2 card will write at speeds higher than 2MB/s.
The only way to be sure of getting a card that will read at a certain speed is to buy the appropriate class.
Step666 said:
That's incorrect - the class rating is a guarantee of both read and write speeds.
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Click to collapse
That's a nice opinion, but unfortunately it's just wrong.
Have a look at this. Notice they dont mention read speeds anywhere, that's because theyre already so fast regardless of class that it's irrelevant.
When you buy a class 10 SD card, youre spending your money on faster writes.
The read speeds of all cards tend to be the same regardless of class.
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Click to collapse
The limiting factor in read speeds is the interface, not the memory technology. I believe SDXC may have faster interface specs than SDHC (which in turn has faster specs than plain SD), but this is nothing to do with class, and make no difference if youre plugging them all into an SDHC device anyway.
Try reading that page again, it doesn't say that the class certification is a measure of writing speed, it says it's the bus-interface speed - it merely mentions write speeds as examples of why you would need higher speeds in real life.
The read speeds that the cards are actually capable of may well be higher but in practice the write speeds are almost always higher too - but there's no guarantee they are.
Step666 said:
Try reading that page again, it doesn't say that the class certification is a measure of writing speed, it says it's the bus-interface speed - it merely mentions write speeds as examples of why you would need higher speeds in real life.
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Click to collapse
So it's just a coincidence that nowhere does anyone mention read speeds, only write speeds and recording, when talking about flash memory. Because nobody's interested in read speeds, right?
Look, the read speeds of flash memory devices are stupidly high compared to write speeds (and always have been), and are limited by the interface, the write speeds are limited by the technology of the memory itself (which is the bit all of the manufacturers have spent millions (probably billions actually) improving over the last 10 years.
I hate quoting wikipedia articles but:
The Speed Class Rating is the official unit of speed measurement for SD Cards, defined by the SD Association. The Class number represents a multiple of 8 Mbits/s (1 MB/s), and meets the least sustained write speeds for a card in a fragmented state.[17]
These are the ratings of all currently available cards:[14][24]
Class 2, 2 MB/s
Class 4, 4 MB/s
Class 6, 6 MB/s
Class 10, 10 MB/s
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I can see this going round in circles. From what I've read, basically, if you put a class 10 card in a phone that has been running a class 2 card then you're not going to see the difference like you would putting 4GB of memory in a PC that has been running on 512MB, but having a higher class of card will improve some areas behind the scenes so to speak.
If I didn't have an X10 to sell then chances are I'd stick with my class 6 Samsung but as I'll have the money to go class 10 I am doing.
daveybaby said:
Look, the read speeds of flash memory devices are stupidly high compared to write speeds...
Click to expand...
Click to collapse
And?
Real-world write speeds on cards are generally higher than their class rating would suggest but you are only guaranteed the speed corresponding to the class the card is.
Exactly the same applies to read speeds, they will most likely be much higher in real life but you are only guaranteed the speed that corresponds to the rated class of the card.
The class of a card guarantees minimum read and write speeds but both will likely be noticeably higher in real life.
Class has nothing to do with read speed period. Manufacturers only guarantees the write speed based on classifications because read speed will only be the same for all class of cards. Try the "Sd Tools" app if you don't believe me.
Therefore, unless you are using the defunct "app2sd+ data, dalvik", there should not be any discerning difference except for its higher price.
Sent from my LT15i using XDA App
Step666 said:
And?
Click to expand...
Click to collapse
And the read speed limit is defined by the interface implementation not by the class of the card. When i say flash read speeds (i.e. reading data from the cell) are fast, i mean theyre to all intents and purposes instantaneous, they always have been - they havent gotten any faster in the last 20 years - it's inherent in the technology. The thing that takes all the time is shuffling the bits of data across the serial interface.
It's entirely possible for a class 2 card by one maufacturer to have faster read speeds than a class 10 card by another manufacturer. It's entirely possible for the same card to have different read speeds in different devices due to the interaction of the interface implementations (subtle timing differences). Write speeds arent affected by this as much because the bottleneck is the large amount of time it takes to erase a cell and rewrite it.
Note that if you have a really old class 2 card, it's probably going to have much slower read speeds than a brand new class 10 card. This is not inherently due to the class of the card, it has everything to do with the fact that manufacturers only implemented faster interfaces to handle class 10 cards once the technology to *write* at this speed became available. Due to economies of scale they implement these faster interfaces across the board. New class 2 cards will be able to read as fast as new class 10 cards.
That's all i'm going to say on this matter, if you dont believe me you dont believe me, i'll agree to disagree.
daveybaby said:
That's all i'm going to say on this matter, if you dont believe me you dont believe me, i'll agree to disagree.
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I'm afraid I don't, we'll have to disagree.
The sdhc that came in the box has a class 2 rating in it but using sd tools, it writes at 6mb/sec average, bursting at 9mb/sec. Read speed is the same as my older 8Gb class 6 at 19-20mb/sec.
Step666 said:
I'm afraid I don't, we'll have to disagree.
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Cool
I have Sandisk Micro HDSD 16GB Class 2 but in SD Tools Write Speed: 10.1Mb/s, Read Speed: 27.5Mb/s

What is difference in SD card classes

Ok I have an Acer Iconia a500, currently I have only a 6gb card installed. Now when i look online i see that the micro sd cards are rated by classes. What is that for?
I need a 32gb for my Iconia. I do alot of school work from it. Just want the storage for my school books. any way, can someone break it down for me?
Thank You
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The SD card's class represents the least write speed.
Class 2: 2MB/s
class 4 : 4MB/s
and so on..
I think it's so you can copy and read files faster
ok, got it, higher the class the faster the write speed.
One more thing, now, the higher the class, does anyone know if they have more problems? like with crashing, or having to be re formatted often?
primus123 said:
ok, got it, higher the class the faster the write speed.
One more thing, now, the higher the class, does anyone know if they have more problems? like with crashing, or having to be re formatted often?
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Nope, problems/crashing etc would be down to quality not size.
Also faster write speed doesn't mean it performs faster when used as a "hard drive" like in a phone, so lower class ones can outperform higher, but you'd have to try them to see.
It's because they're designed with things like cameras in mind, where getting the image saved quickly so you can take another one is the most important thing.
In a mobile phone/tablet they're accessed more randomly, and that is where it's been found that some higher class cards don't perform as well.
Mini SD cards, so tiny for my big hands.
Those mini sd cards are SOOOOO small, I've lost a few over the past 3 years.
so which one should i get for my iconia
androidappdeveloper said:
Those mini sd cards are SOOOOO small, I've lost a few over the past 3 years.
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Tell me about it, I just reordered one after giving up the search on my current one. It's not completely lost, I'll probably come across it one day when re-organizing the room.
I keep mine in those Sd card cases and shove it in a crown royal bag....
You're probably fine with a Class 2 microSD card, as you won't have large files (or a large amount of small files) written in a short time.
Write speeds are generally the most important feature of a memory card. Write speeds determine the amount of time it takes to transfer the data, the moment you for example, click the button on your camera to ask the camera to take the image. You will probably remember that back in the early days of SD memory cards, there was an awful amount of lag time on cards, i.e from when you heard the click on the button (when you asked your camera to take the picture), to when you heard the double click (which is normally when the image has been written to the card).
Read speeds indicate the amount of time it takes for a card to transfer the data to a PC/Laptop. I.e the amount of time it takes to read the data off the card. Generally the higher the capacity of the card, this will naturally give a higher write speed. So if you have a 32GB card full of data and its only a class 2, it would take much longer than a 32GB card thats class 10, to send all the info to your pc etc.
Class 10 cards are recommended for HD video, or minimum class 6 really. You will probably find a 16GB class 4 card for example, will not work on say a Samsung HD Camcorder. It will maybe store only 1 minute of video, as for some reason the HD cannot write the data to the card fast enough it would seem.
Anyone ever lose a mini SDK card?
Plus your SD class is high, more it is fast...
jerryfranks said:
Anyone ever lose a mini SDK card?
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Yes, almost (I found it after w hile), bloody spring so strong it shot across the room!
Pity there's not some little leatherette folder with tiny slots for a few MicroSD cards, I'd buy one!.
iloveapple said:
Write speeds are generally the most important feature of a memory card. Write speeds determine the amount of time it takes to transfer the data, the moment you for example, click the button on your camera to ask the camera to take the image. You will probably remember that back in the early days of SD memory cards, there was an awful amount of lag time on cards, i.e from when you heard the click on the button (when you asked your camera to take the picture), to when you heard the double click (which is normally when the image has been written to the card).
Read speeds indicate the amount of time it takes for a card to transfer the data to a PC/Laptop. I.e the amount of time it takes to read the data off the card. Generally the higher the capacity of the card, this will naturally give a higher write speed. So if you have a 32GB card full of data and its only a class 2, it would take much longer than a 32GB card thats class 10, to send all the info to your pc etc.
Class 10 cards are recommended for HD video, or minimum class 6 really. You will probably find a 16GB class 4 card for example, will not work on say a Samsung HD Camcorder. It will maybe store only 1 minute of video, as for some reason the HD cannot write the data to the card fast enough it would seem.
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Very helpfully post,thanks.
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Try to continue promoting of you site.
Hi speed cards are more efficient at presenting and recording. It's really up to you. If you buy the cheaper version and it doesn't present at the speed you think it should you'll have answered your own question.
You guys have it mostly right. The higher class your card is the faster it can write a file to its memory, the trade off is that the higher class cards have slower rapid access speeds, something to do with how it prepares files before writing. Basically, a class 10 will write a 1GB file faster, but if you try to write 15 3MB files quickly your performance will suffer. For something like a phone I recommend a class 4 or 6. For cameras I'd go higher (I don't know a whole lot about cameras).
seems like its good

[Q] SD Card Speed?

I just got my new 32GB Class 4 SD card, and was shocked to see that the write speed was nearly half the speed of the SD card that came with the phone, which turned out to be a Class 6. But what confuses me most of all is that a higher class should be faster if I'm correct, and the write speed of my new SD class is slower, but the read speed is actually faster. I'm seriously confused as to if this is what is meant to happen. >.<
Speeds of MicroSD cards tend to fluctuate, especially under the Android environment. You may have tested when the Class 4 was at peak read speeds, and when the Class 6 was at low read speeds
But it wasnt just one test, I tested the Class 6 multiple times and was getting 13 - 14mb read, and the Class 4 got 19mb+
>.<
Did you takes all those tests in a row? Or on separate occasions? My class 6 Sandisk got above 28mbps reads even on Android
Seeing as though you got 28mbps, Im starting to wonder whether my SD cards are faulty, my phone is faulty or something else. >.<
In addition, you'll also see different speeds when using cards of different brands. However, high sequential read/write speeds aren't always what you should be looking for. If you run ROMs from SD or have lots of apps installed to your SD, you should also consider looking at the random read write/speeds as those speeds are more important for those aspects.
If your new sd card is a larger storage it will be slower because it has more data to check through if they are the same size you may have even got a dodgy sd card or fake there is lots of reasons why this can happen and as solar plexus said
Solar.Plexus said:
In addition, you'll also see different speeds when using cards of different brands. However, high sequential read/write speeds aren't always what you should be looking for. If you run ROMs from SD or have lots of apps installed to your SD, you should also consider looking at the random read write/speeds as those speeds are more important for those aspects.
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