Micro SDCard Recommended?

[OptoMan]

I’ve got a couple rules of thumb but there’s a bit of juju, some of that first even — I’ve seen some posts about sd’s that are too fast for chinese tablets — that’s a touchy subject that almost makes no sense — here’s my recommendation ..

name brand, newer item.  speed class on older models are a number less than or equal to 10.  and it’s that many MB/s.  yes, bytes =)  newer ones are by ‘class’ but by UHS rating which is tens of MBs.  so, UHS-1 is supposed to be the same speed as Class-10.  newer is better when it comes to quality and technology in general — the gotcha is capacity.  higher capacity flash chips have higher density, as in smaller process, more bits stored in same volume.  easier for those to break.

next up is what else is in the sd card besides the memory itself — a small microcontroller that translates where the OS thinks it’s storing something and where the sd card ends up putting it.  wear-leveling is what they call the method of spreading use of the storage over the whole thing — example would be if you had a 32 GB card and only used it for a small task that required a typical 500 MB.  wear-leveling will use differend parts of the chip instead of the beginning every time.  it’s has algorithms it follows and such.  microcontroller also keeps track of bad sectors as the occur, and you could and should consider scanning the device for bad-blocks with your operating system so they get marked on the filesystem level as well — after doing this a few times consider retiring the card if your kind of use is formatting and using, formatting then using.  hope that makes sense.  supposed to have a lifespan in the 10s of thousands of RW cycles .. but things happen, and smaller things have more bad things happen.

back to the microcontroller — this seems to be what dies the most, from my perspective — on a large percentage of sd’s there are some parts of our [traditionally-viewed] storage that only the microcontroller cares about, and is inaccessible from anything outside the card — when this stuff gets corrupt, it can os-so-rarely be changed.  the mistake was from the microcontroller however.  whether it just made a non-oft mistake or is starting to exhibit problems doesn’t really matter — so quality of the microcontroller.  brand, ratings on sites that sell might ought to look at but many people just post away.

last part that is brand specific — number of cache areas.  the number is usually 3-10 and some brands are known to have more than others.  what it’s for is this — when a program has a file open, and is changing it often, you don’t want to re-commit it to flash memory .. so you keep it open somewhere else first.  in fact computers try to do this anyways .. mostly just mess with stuff in ram till it seems a good time to record it to disk.  but think of disk intensive software, especially something like web caches — and their indexes.  flash memory has some funny numbers attributed to it — when you read a piece, you ask for the data in the location — but like all disks, it’s recorded on whats called a cluster  the smallest piece of a file system that can be recorded or read.  (that’s filesystem level, akin to a sector on hardware level).  smaller files will take up a whole cluster regardless.  larger files will take up multiple clusters, with one that probably isn’t full. — back to sd — usually larger than an FS cluster is an actual flash read block.  contains many clusters and/or some empty space.  there’s also a flash record block — *this* is the one that gets us.  record [or write] blocks are usually very large, in megabytes.  so what actually happens is that to share a partially used record block with some new information, the whole block is read, and then to modified to include what you want to record, and records the whole thing back again.  SO — full circle, if we can hold on to some information for a while in this third part of the sd card, the cache, we won’t commit any changes till we think we’re done for a while — cache is way faster.  recording flash is slow.

like I said, some brands prefer to have different number of cache spaces, which almost directly correlates to how many files you intend to have open at once.  more doesn’t necessarily mean better — that might be the only selling point about the thing and it’s microcontroller — but it’s one of the differences that makes on card of a class act totally different than another card of same class.  BUT this all depends on how you use the thing.

almost done so sorry — internal sd on devices is almost always faster than the external sd — that’s some juju.  if you keep from thrashing your external sd with needless software, most any modern name brand sd with a good rating and an appropriate rating should do quite nice.

about the chinese tablets not liking some sd cards — this ain’t even right, because they don’t want to sell something that will stop working — these are real brands — but maybe if something’s set to run full speed all the time — sd lines on the mainboard — this still makes a dumb generalization, not sure what to say.

someone add cause I’m interested too .. also like to say that some peoples’s batteries blow up more than other people’s.

I think what we are definately looking at is some stuff like reported speeds, internal noise (spread spectrum is turned off on a few things on my tablet) and of course misuse/abuse .. asking too much from the microcontroller, like ntfs filessystem instead of fat — btw, windows 10 formats flash terrific.  as good as or better than any fancy sd or usb-thumb format utility.

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