Hello Junjiro & list, On Wed, Nov 30, 2011 at 08:28:39PM +0900, sf...@users.sourceforge.net wrote: > > Klaus Knopper: > > Various approaches, from just creating and deleting files over the file > ::: > > OK. > > > > Like in > > dd if=/dev/urandom of=/dev/sdb oflag=direct,sync bs=131072 > > ? > > Yes, oflag=direct is what I meant. > Even if you applied direct-io, you could not see the write limit on your > flash, right?
I never got a single defective sector yet after several ten thousands of writes, right, so the assumption stated on wikipedia that, at least with common USB sticks and SD cards, an internal controller will manage the physical writes to blocks on these devices, seems to be correct. Here is a reference to tests that Heise Magazine did, which yields the same result (they were not able to kill an USB stick even when rewriting the same logical address 16 million times): http://www.heise.de/ct/hotline/Flash-Haltbarkeit-296140.html However, power failure or removal of media during a write, regularly caused random defects (mostly complete loss of capacity), so this seems to be the drawback of "intelligent" write block handling vs. software-side-only wear leveling and defective block management. Also, flash media ages. Manufacturers only guarantee cells to hold the information up to 10 years, so, flash is probably not good for long term storage. Well... Similar problem for magnetical or optical storage, which make it up to 50 years only. Printed paper lasts much longer. But that is a different topic. ;-) > > ... I think that using aufs only for > > saving write cycles on the physical storage device is not the perfect > > way to go, especially when RAM and CPU power are tight. > > Agreed. > And I have suggested "tovis" NOT to use aufs for such purpose. aufs is good for a lot of other things. :-) Regards -Klaus ------------------------------------------------------------------------------ All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-novd2d
