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USB Flash Drive Life Varies Up To 10 Times
Lucas123 writes "Differences in the type of memory and I/O controllers used in USB drives can make one device perform two or three times faster and last 10 times longer than another, even if both sport the USB 2.0 logo, according to a Computerworld story. While a slow USB drive may be fine for moving a few dozen megabytes of files around, when you get into larger data transfers, that's when bandwidth contrictions become noticeable. In 2009, controller manufacturers are expected to begin shipping drives with dual- and even four-channel controllers, which will increase speeds even for slower drives."
Yes, there is. But those are designed for raw access to the flash medium. The drive's controller provides a facade of having a whatever you formatted it as.
Why is it every other media we have speed-ratings and benchmarks and reviews? With USB thumb-drives you can't tell virtually anything when purchasing one other than what color it is.
I want to know SOMETHING like 133x is defined for CompactFlash to give a basic idea of the speed of the device. I'm willing to accept some fudging around but not prepared to find out my new 32-gig flash-drive is 10 times SLOWER than my old 2-gig one. How has this situation persisted this long in a performance-obsessed technical field?
Then I copied a 700 MB file onto it from a local hard drive in gnome, which reported initially that it was transferring at 20+ MB/s, but that dropped steadily until it levelled off around 6.1 MB/s.
Far from scientific, yes, but I wonder a)why the inconsistencies, and b)how these results compare with other products.
db
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I installed Arch Linux on a cheap 2 GB Patriot flash drive. It boots pretty quickly and overall performance seems good, even for a cheap drive. However I don't do hugely disk intensive tasks with it.
/proc filesystem entries to turn more aggressive write cache flushing on. I can't keep up with the /proc filesystem because it changes so frequently, so I don't even bother to try to stay abreast of how to do things with the Linux kernel in this way anymore ...
One annoying thing I have noticed is that programs will periodically completely freeze up and I'll look over and notice that the activity light on the drive is flashing. A common experience is that Firefox will be completely unresponsive, not even redrawing itself when a window that was obscuring it is moved, until the drive stops flashing, and then Firefox will instantly come back to life.
My theory is that the kernel is caching writes to the drive and then at some random point decides it's time to flush the write cache to disk. I think that any program that tries to write any files while the kernel is flushing the cache gets put into a wait state by the kernel until the cache flush is complete and then whatever write the program was attempting, gets written into the cache, ready to be flushed again on the next cache flush.
Furthermore, I theorize that for normal hard disk drives, the write speed is sufficient to keep "ahead" of cache flushes so that the cache never really "fills up" and no programs ever get waited in this way.
But that for slowish flash drives like mine, the kernel doesn't compensate for the slow write speed of the flash (because the kernel doesn't even realize that it's writing to flash?) and so it lets enough data buffer up that it has to frantically try to flush it all when the cache has filled up. Or perhaps, that the kernel just tries to flush too much at once, not realizing how slow the flush is going to be due to the underlying speed of the device.
I also theorize that this problem could be solved by having the kernel flush the cache more aggressively, and in smaller increments. If the flash drive were kept continually busy flushing small chunks of write cache, then a) the write cache would not be as likely to fill up, and b) no individual write would monopolize the device for such a long period of time becase the writes are all smaller.
Writing all of this makes me realize that the root cause may be that programs are trying to *read* from the device while a write cache flush is happening, and since the device can only do one operation (read or write) at a time, the long duration of the cache flush operation is blocking a program from reading the drive. Furthermore, if what the program is trying to read is a demand-paged part of its text segment, then it makes perfect sense that the whole process would be blocked by the kernel while the text segment piece waits to be loaded.
Am I even close to the mark on this one?
If so, I am sure there are Linux kernel experts who can tell me what values to write into what
echo -e 'global _start\n _start:\n mov eax, 2\n int 80h\n jmp _start' > a.asm; nasm a.asm -f elf; ld a.o -o a;
Whoops, typo :) But your response was funny.
:) Of course you'd have to take the USB 2.0 spec back with you too ...
...
This does remind me of what a geek I am though. I think I must be the only person in the world who often daydreams (when I have the time and inclination to daydream) that I've gone back in time and taken some piece of modern computer equipment to shock and amaze people from the early days of computing.
For example, I'll daydream that I've taken my laptop (which is now a few years old and not impressive to anybody, but with 768 MB of RAM, a 40 GB disk, and 1.4 Ghz Pentium M, would have blown the socks off of a computer enthusiast from, say, 1969) back in time and am showing it off to a group of scientists like at say that famous "mother of all demos" where the mouse and graphical interface were first demoed.
Can you imagine showing up and being like, hey check this out. That 64 KB PDP-11 that you have running your demo is cool and all. But let me show you my computer, which has 768 MILLION bytes of RAM! And a 1400x1050 32 bit color flat panel LCD display! With built-in keyboard!
It's not that I would lord it over anyone. But it's fun (for me) to daydream about the conversations you'd have with someone from 1969, explaining to them the advances of modern technology and how they are used in our world.
Anyway, your comment reminded me of that, because although a 2 GB flash drive today is totally ho-hum, if you could sneak one of those back in time to the 1970's, you'd have something that governments would probably go to war over
Like I said, I am a total geek
echo -e 'global _start\n _start:\n mov eax, 2\n int 80h\n jmp _start' > a.asm; nasm a.asm -f elf; ld a.o -o a;
Cowon A3, it supports more media formats than any MP3 player out (ogg, flak, mkv) there and you can read directly from a USB thumb drives. As a MP3 player the Cowon A3's audio quality blows the iPOD right out of the water, even has a 10 channel equaliser built in.
>I thought everyone knew that you get what you pay for, both speed and durability.
Sure, you get what you pay for. But the problem here is that these drives don't indicate on the packaging whether they use SLC or MLC memory, or whether they offer more than one channel.
So let's say the crappy variety of 4 GB USB drives currently go for $25, and the better, faster variety will never sell at that price. Right now, you have no way of knowing whether that 4 GB drive going for $50 is made with the faster, more durable SLC memory, or whether the drive is simply overpriced.
You can therefore spend $50 for a drive and not get what you paid for. And the only way to safeguard yourself is to waste time researching your drive -- something you shouldn't have to do, since this info ought to be published as part of the drive's specifications.
I'm generally "Interesting," "Insightful," and even "Funny" here. What the hell happens to me at parties?
I have always wondered why no one has mad a USB thumb drive with a flexible/swivel neck. Ive seen a few laptops with the USB sockets damaged after a user has connected the thumb drive then forgotten about it and then knocked it (thus cold soldering the laptops USB socket).
Mod parent up! This is the heart of the problem right there: manufacturers don't write whether the USB drive (or SD card, or any other Flash RAM device) uses SLC or MLC Flash RAM. But that's the main difference. SLC Flash will survive 100.000 write/erase cycles, MLC only about 5000. That's a HUGE difference. Especially if you use the USB drive to host an OS that likes logging a lot. Each log write implies the whole Flash RAM block (usually 128 KB) to be erased and then written to.
Logging is the Flash RAM killer.
And Kingston and Sandisk should start putting "SLC" or "MLC" on their products, so we techies know whether they are worth the double price.
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I was just discussing this the other day, and my friend found this: http://www.kingston.com/ukroot/flash/flashendurance.asp
Escher was the first MC and Giger invented the HR department.