What are classes on SD cards?

All I know is it has to do with the speed and I/O. Lol, is higher better or lower? WHat's applicable for an android phone storage card?

 

it should be the speed of the minimum write speed. higher is faster. but higher doesn't mean better. not all cards/brands are created equal. and for instance, sandisks are usually reliable and perform above their quoted class speed. class 10 cards on micro sd's are kind of a gamble. not many perform up to the task and usually aren't very reliable.

 

If you're using it in a phone you really won't need anything more than a class 4. Class 10 is wasted inside a phone. The only benefit from a class 10 is if you transfer files directly between the card and computer.

 

the class thing is just marketing. search for real life benchmarks of read write. and beware of counterfeit cards.
What a non sense to say class10 is wasted. I transfer at least 4gb of data each day. It would be painful if I hadn't a fast card.
Random 4k reads are very important because cell phones are full of very very small files. so if you have a a slow card your apps will be slower. But if a card has a benchmark of let's say 20mb/s it doesn't mean it's faster in 4k then another card benchmarked at 10mb/s.
Formating the card to an higher cluster size will also improve it's performance (and will also reduce a bit it's capacity).

 

I have Debian running from a 32GB microSD card on my smartphone and I wouldn't want to run that on a class 4 card.

 

Which phone are you using? Something like this?




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Anyone know of a reliable fast-enough card who has hands on experience with it and a smartphone?

 

Class 6 or higher is what I go with, but even lower is fine for phone use unless your like planning to record HD movies or something.

Often lower class cards out preform higher class cards in real life testing just due to how they handled random read/write vs continuous read/write and other factors.

 

I have a Samsung class 2 in my phone (no HD camera though) and a Sandisk class 4 in my nook (running CM7 entirely off of the card). Both are fast enough for the devices they are in.

 

source: http://forums.whirlpool.net.au/archive/1582172

source: Benchmark Results: Random Reads And Writes : Round-Up: 15 microSDHC Cards, Benchmarked And Reviewed

 

The class 4 card I have in my phone works just fine for my uses. I had tried a class 10 card and I didn't notice any significant increase in performance. As such I sold it and stuck with the class 4. I simply can't justify the extra cost for my applications.

 

like it was said. class thing is PURE MARKETING. just check the benchmarks. I've some class 4 cards that perform way better then class 10 ones.

 

Guys, is the 4GB Sandisk mobile ultra microSD card one of the best around for read speeds? (read speeds in spec up to 30mb/sec). I want to put full Great Britain 1:50k OS mapping on my newly acquired garmin extrex 30 gps and can only do this via a microsd card (not enough internal memory of gps) so want a card which has fast read speeds.

 

I'm running an OS (CM7) off of a Sandisk class 4 (32gb) card currently, and it doesn't run any differently than if I ran it off my tablet's internal storage. So I'd say you shouldn't have a problem. From what I've heard, Sandisk cards of any class are good at random read/write (4k >1mb/s, which is better than most hard drives), which is what you want if you're running an OS off of it.

 

Sorry I meant Ordnance Survey Mapping, not Operating System

 

i think sandisk doesn't print speeds on their cards anymore but you might be able to find the ones where they did print 2 and 4. it would be preferable if you got one printed with a 4. a bigger card might, keyword might perform better. nonetheless, if you do score one without a class be assured that it will probably run well beyond 4 except for smaller files. smaller files are the doozies. sandisk are usually very reliable cards i might add. i tend to get transcend or lexar cards for preference. transcend is a good all around performer and pretty reliable and has treated me well the last few years. lexar cards are usually faster than what they are rated but they're reliability sometimes suffers. i'd stay away from 10 class cards if speed isn't high priority. lexar would be the safest bet on that though.