I'm confused on the Class rating for SD cards. I understand it to be a write-speed rating, and in my usage I'm more concerned with read throughput. My goal is to watch 480p and 720p content without jitters, and I'm not sure if the higher class matters or not for reads.
Thanks!
The write speed is going to be the same as the read speed. With flash memory fragmentation doesn't effect read speed much because of the low access time. With writing the card has to find an empty cell and write which could effect the writing performance. The class signifies that under heavy fragmentation the card should write at the speed of the class (i.e. class 10 should be 10 Mb/s). Also, regardless of fragmentation the card should read at the speed of the class. So in your case if your not needing high speed write then a class 2 or 4 should be fine. I personally wouldn't go below 4 because you never know if you might need the extra speed later.
Looking at Wikipedia the class is both Read & Write.
I personally use class 4 16GB cards and they seem to do the job fine on the re-encoded 1080/720 content I have on them.
I have a Class 10 Patriot Micro SDHC card and it works fine. I also tested with a Patriot SDHC (full size) in the sock and works fine. Both tested with 720p H264 MOV.
Heh I would be worried if a class 10 (being the fastest you can get) was having issues
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a class 10 is perfect for anything and ull only spend another maybe 10then a class 4. i only get class 10s or higher for my phones and cameras just in case i need the extra power
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Full size SD's are pretty similar in price between classes but microSD's are insanely different... £17 for a class4 16GB or £40 for class10
alex5790 said:
The write speed is going to be the same as the read speed. With flash memory fragmentation doesn't effect read speed much because of the low access time. With writing the card has to find an empty cell and write which could effect the writing performance. The class signifies that under heavy fragmentation the card should write at the speed of the class (i.e. class 10 should be 10 Mb/s). Also, regardless of fragmentation the card should read at the speed of the class. So in your case if your not needing high speed write then a class 2 or 4 should be fine. I personally wouldn't go below 4 because you never know if you might need the extra speed later.
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No. The class is the garunteed write speed, the read speed has no relation and can vary from card to card. I am using one of two cards in my tab, one a class 4 and the other a class 2 and neither have ever come close to having an issue streaming. The class 4 can read at over 16mb/s, Ive tested it.
The only reason to pay for a C6 or higher card is because you need to push data to it quickly., like recording video.
ryan stewart said:
No. The class is the garunteed write speed, the read speed has no relation and can vary from card to card. I am using one of two cards in my tab, one a class 4 and the other a class 2 and neither have ever come close to having an issue streaming. The class 4 can read at over 16mb/s, Ive tested it.
The only reason to pay for a C6 or higher card is because you need to push data to it quickly., like recording video.
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+1. This is the correct answer. Good cards typically read much faster than the write speed.
Read speed is not correlated to the write speed or class rating at all...and in most cases, it's way higher than the write speed...
so theoretically even a class 1 card (if you can find one) is able to stream 720P content without much issues..but it will take forever to copy the content onto the card.
my class 10 card reads over 30MB/s and my class 4 does around 16MB/s
What card do you have? I was looking into getting one.
Related
I'm familiar with the difference between the class 4 (4MB/s transfer speed) and the class 6 (6MB/s transfer speed). But is there any value in using a class 6 card on the XV6800 (regardless of size)?
I ask because I have a 4GB class 6 A-Data microSDHC card in my XV6800 right now and there is no problem at all with it. However, I am considering purchasing an 8GB class 4 Sandisk microSDHC card. So it got me thinking, even thought the A-Data card is capable of a faster transfer speed, that doesn't mean the XV6800 is ever actually using that extra speed. So would I see any slowdown if I moved to a "slower" spec'd microsdhc card?
I looked around for transfer speeds on the XV6800's microSD card slot and didn't come across anything.
Anyway have any data on this? Thanks in advance.
Depends some on what you are using it for but I doubt you will notice much of a difference. When transferring using a card and a card reader from your computer you may notice a difference but otherwise the interface in the phone itself doesn't seem to be all that fast anyway.
Don't get me wrong, I appreciate the comment, but that's why I'm asking if anyone has any actual data. The device either reads and writes to the microsd card slot above 4MB/s or it does not. I have not found a way to benchmark it so I'm looking for some actual detail. But thank you.
So I found an application that is supposed to measure the transfer speeds of the card slot on a Windows Mobile device. It's from Audacity Audio. The link on Softpedia is here.
I'm familiar with the application because I used the Palm OS version on my old Treo 700P. The problem is that he results always seem inconsistent and confusing.
In any event, I ran the test on two different microSD cards. The first is an empty 1GB Sandisk microSD card with. These cards don't have a "class" rating. The second is a 4GB AData Class 6 microSDHC card. I still had 2.5GB of the 4GB empty.
1GB
Wrt32bit/Wrt8KB/Read8KB
1105/330572/7943757
1105/335208/7710117
1123/366634/7710117
1030/311705/7489828
1070/306242/7489828
Avg
1086/330072/7668729
4GB
1462/109317/6393756
527/111408/6241523
1462/119482/4161015
517/85724/6241523
1581/126334/6241523
Avg
1109/110453/5855868
Honestly, the scores don't seem to make much sense. The read speeds all indicate north of 4MB/s and most of the time above 6MB/s. That's good. But the write speeds seem pointless. 330KB/s (.3MB/s) for the 1GB and 110KB/s (.1MB/s) for the 4GB ?!?!?! That doesn't seem right.
Anyway, any ideas would be welcome.
Write speeds are typically going to be a great deal slower for flash memory. And larger cards being even slower for writing makes a twisted sort of sense. All flash cards have "load-leveling" algorithms built into them to spread the writes across the flash disk in order to reuse locations as little as possible (flash memory cells have a limited lifetime). So the bigger the card, the more memory the load leveler has to manage. Of course, I could have it completely wrong....
So here is the question.Untill what speed can the cardreader of the Hero support?Class 2,4 or 6?Is there any point on getting a card above lvl2 for a phone anyway?I mean right now i have the default card on it and still i can see movies,photos play music etc pretty good without problems.Why should i choose class 4 or even class 6?
At the moment i found class 2 micro SD 16 giga for 25 euro and class 6 8giga for 19-20.Which should i pick?I am pretty sure that i can use even 16giga of data space but i am not sure if i can use higher speed rates than class 2.
You can choose any class of SD card you want, but the class 6 is faster and gives better performance. Trancend also have a 16GB class 6 card.
well i know that class 6 is faster.What i ask is if Hero can handle the speed or Class 4 or Class 6 and if there will be any real diference in performance.If yes in what application, since music , pics or even movies play good enouph in even class 2 cards.
You will notice it if you use Apps2SD and have a swap partition on your SD-card. Otherwise you won't notice the difference I guess.
Ludolf71 said:
You can choose any class of SD card you want, but the class 6 is faster and gives better performance. Trancend also have a 16GB class 6 card.
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This is a common misconception. A class 6 card is not necessarily faster than a class 2 card, because all that the class signifies is the *minimum* guaranteed sustained speed that a card can be written at.
It is perfectly possible for a class 2 card to outperform the minimums required for a class 6 card, so that a good quality class 2 card can be faster than a poor quality class 6 card.
My advice when buying an SD card is to look for independent reviews where the actual speeds are tested. For example, see here.
Regards,
Dave
foxmeister said:
This is a common misconception. A class 6 card is not necessarily faster than a class 2 card, because all that the class signifies is the *minimum* guaranteed sustained speed that a card can be written at.
It is perfectly possible for a class 2 card to outperform the minimums required for a class 6 card, so that a good quality class 2 card can be faster than a poor quality class 6 card.
My advice when buying an SD card is to look for independent reviews where the actual speeds are tested. For example, see here.
Regards,
Dave
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Very interesting
A friend of mine just bought a Galaxy SII and wants to know if it's worth getting a class 10 card. Can the phone write to the SD at that speed. What is the maximum speed the phone can write to the card at?
The question is what you are planning to do with your phone to make use of such a high speed.
Class 4 means a writing-speed of at least 4MB/s. Even ignoring the fact that most cards can write significant faster in reality than their Class indicates, there is nothing you can really do with a phone to use this speed.
The fastest writing-speed you will need is when recording movies, and the highest bitrate the default camera uses is 17MBit/s.
With a Class 4 card you can record at least 32MBit/s.
Of course you can transfer your media faster on your card, if the writing-speed is higher, but how important is that?
It is a good point put forward by the poster above.
I have a class 10 card and it only comes in handy when transferring files to and from the card. Transfer speed is about 14MB/s with a patriot clss 10 16 GB from my experience so appears to be limited by the speed of the card. And writing is over 10MB/s which the class 10 part defines.
hey all, i was just wondering if anyone knows the differences between the tests that crystaldiskmark does to test the speed of a storage device.
there are 4 different tests: sequential, 512k, 4k, and 4kQD32. read and write tests for each type of test.
thanks!
EDIT: heres a screenshot of my results:
I can't tell you about all of them, but sequential writes are what your card class is all about. A class X card is supposed to write a minimum of X MB/s. Your class 6 is writing well above its rating, congrats.
The other I can mention is 4kQD32 writes -- according to the Nook Color folks, it's very helpful for performance of SD installs of Android, so if we ever get an sd install here, hold on to that card. Higher class cards, 6 and 10, often do horrible in that 4k writes category. Class 2 and 4 Sandisks seem to have the best track record, but your transcend isn't half bad, and my best 4k writer is a no name card that outperforms my other 2 sandisks and a samsung. Source.
fortunz said:
I can't tell you about all of them, but sequential writes are what your card class is all about. A class X card is supposed to write a minimum of X MB/s. Your class 6 is writing well above its rating, congrats.
The other I can mention is 4kQD32 writes -- according to the Nook Color folks, it's very helpful for performance of SD installs of Android, so if we ever get an sd install here, hold on to that card. Higher class cards, 6 and 10, often do horrible in that 4k writes category. Class 2 and 4 Sandisks seem to have the best track record, but your transcend isn't half bad, and my best 4k writer is a no name card that outperforms my other 2 sandisks and a samsung. Source.
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All right thanks. Its weird though I was just trying to copy a huge amount of files to my sd card (about 6.5 gb) and it was writing at like 3 mb's per second. Does the size of the transfer affect the write speed since this test was only using a 50 mb file?
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Copying lots of little files, in my experience, goes slower than copying a single large file. When I copy a video onto my card, I get close to the max speed. When I copy directories full of files, anything goes.
fortunz said:
Copying lots of little files, in my experience, goes slower than copying a single large file. When I copy a video onto my card, I get close to the max speed. When I copy directories full of files, anything goes.
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Ok well I guess this sd card isn't all too bad then... really wanting to get a 32 gb card but trying to wait until I can get a better deal for it... you think a sandisk class 4 32 gb is good enough for games and videos?? I haven't seen any class 6 32 gb cards anywhere... not even sure if they exist...
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ShinnAsuka said:
you think a sandisk class 4 32 gb is good enough for games and videos??
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I have a SanDisk Class 4 32 gb card for my Nook Tablet and it seems to work fine for games like GTA3, Angry Birds, etc. as well as .avi movies.
I tend to agree with Nookie. Depending on its actual performance (sandisks often outperform their minimum write rating, but not always), it might be frustrating to copy the files over, but viewing videos and playing games will work just fine even on a class 2. Fast sequential read speeds are easy to come by, and frankly they don't have to be all that fast to view even HD video. Your games are going to load into ram and play from there and perform just fine.
Hey Guys
Am looking for a suitable Microsd Class rating ( am going for Sandisk, 16 GB or 8GB) for my Motorola Photon. I am going to install a lot of games, specially those Tegra 2 ones, Max Payne and others too, and alot of apps on the phone.And i might use Link2SD to move them to the SD card to keep Phone memory less occupied.
So as to what i feel is that i'd be requiring good read/write speeds for games, plus proper loading of apps (in time, i don't want lags at all). the problem is, according to the Price, i can go for 8GB class 6 or 16GB class 4. What do u guys think i should go for? would it really matter? i know class ratings are the Writing Speeds, but who knows?
Regards
Save up for a Class 10. There is a world of difference between a class 4 and a class 10 especially when using ROMs that have the SDSpeed tweaks.
I like class 4 personally as write speed really only affects installing imho. lower write cards tend to have higher read as well. SanDisk as a brand makes Damn fine cards which I think brand makes more difference than class overall.
Sent from my mopho
@Loki,
What about a Sandisk 8 or 16GB Ultra at UHS 1 speed?
i read the following on Wikipedia about UHS Cards
"Cards that comply with UHS show UHS-I or UHS-II on the label, and report this capability to the host device. Use of UHS requires that the host device command the card to drop from 3.3-volt to 1.8-volt operation and select the 4-bit transfer mode".
Is above compliant with Motorola Photon? I cant seem to find a Sandisk card with a Class 10 rating else than this one.
@Cornelius,
i think that when playing a game, the Phone might want to Read/Write data during play times even.Reading happens all the time, but Writing would also take place. But as Loki said, i'd be interested in trying these ROMs with SDSpeed tweaks. i really want no lags at all...
Regards
it really depends on the game, but writes happen way less than reads in most cases. class 10 is more for pictures and videos in my humble opinion. most games were it matters, it's a 400+ mb 1 Time download and then massive reads.
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@Cornelius
What about apps? they would also be fine with Class 4? i use a Sandisk 16GB class 4 in my Sansa Fuze all the time, and never had a problem with it, but i dont want my phone to lag at all. Apps might need to Read and Write in real time right??
Regards
if finances are an issue, than here is a G Skill brand 32gb class 6 for $15 shipped.
http://www.newegg.com/Product/Produ...ction-_-cables-_-na-_-na&Item=N82E16820231603
usually in 99.99% of cases read is more important than write. usually writes are so small they don't matter.
Sent from my mopho
Lexar 32GB Class 10 $26
I'm averaging 11MB Write and 21MB Read on Imperium Initiatve
high write or high read its always a compromise. if your that worried about hints of lag use the smallest sdcard you can get by with.
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@Lokifish Marz
One suggestion was Class 10 microSD, and when paired up with ROMs that have SDSpeed tweaks, where does the difference lie (imagining u have experiences with class 10 and SDSpeed tweaks)? What is better than when a class 4 is used?
Plus what tool do u use to get the Read/Write speeds? i suppose its on ur phone only? Also i am thinking of pulling the trigger on an 8GB Class 10 Sandisk. I live in India and Amazon is not an option.....only ebay.in is....
@Cornelius, i agree with what u say about reading going on way more than writing, but then what about SSDs in computers? the performance boost is just because of the Increase in read speeds and not write? I know it gets pretty complex in computers, swap and pagefiles, etc, but faster HDDs mean faster computers, and even though writing happens lesser than reading on the phones, but some writing must be happening that bottlenecks the speed of the phone. am i Right? just trying to learn here from u guys.
Regards
no I'm saying a class 4 usually has a higher read speed than a class 10 but yes the big boost from ssd hdd is the read in 99% of cases.
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psgarcha92 said:
@Lokifish Marz
One suggestion was Class 10 microSD, and when paired up with ROMs that have SDSpeed tweaks, where does the difference lie (imagining u have experiences with class 10 and SDSpeed tweaks)? What is better than when a class 4 is used?
Plus what tool do u use to get the Read/Write speeds? i suppose its on ur phone only? Also i am thinking of pulling the trigger on an 8GB Class 10 Sandisk. I live in India and Amazon is not an option.....only ebay.in is....
@Cornelius, i agree with what u say about reading going on way more than writing, but then what about SSDs in computers? the performance boost is just because of the Increase in read speeds and not write? I know it gets pretty complex in computers, swap and pagefiles, etc, but faster HDDs mean faster computers, and even though writing happens lesser than reading on the phones, but some writing must be happening that bottlenecks the speed of the phone. am i Right? just trying to learn here from u guys.
Regards
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I am not sure what class 4 Cornelius is using. I don't have one but do have a class 6 Lexar from the same family as my class 10. On Imperium, the class 6 was slower than the class 10 in every aspect:
Lexar 8GB
class 6
Write- 5.8MB/s
Read- 18.8MB/s
The SDpeed tweaks, when set up correctly, improve read speeds across the board. It does tend to max out at a read speed of 20-25MB/s on Imperium. Further tuning may improve this but haven't had the time. I haven't tried any of the UHS cards yet. The big drawback with lower class cards is going to be your write speeds, the falloff on write speeds is there but not as much.
I'm not saying that Cornelius is wrong, just in my personal experience with flash storage has been different. Having used flash storage as everything from regular use to building flash storage based workstations, the lower class rating has a noticeable impact on write speeds but not so noticeable impact on read speeds on a tuned setup.
I only use SanDisk cards, used to go Kingston but they kinda fell out a while back.
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I'm using the newer Samsung cards and they make quality memory as well. As cheap as a class 10 card can be had why not go for that over a lower class card?