On Sun, 2011-05-08 at 12:26 +0300, shimi wrote: > On Sun, May 8, 2011 at 12:01 PM, guy keren <c...@actcom.co.il> wrote: > On Sun, 2011-05-08 at 09:57 +0300, shimi wrote: > > > what tends to get worse after the SSD becomes full is writes, > not reads. > and combinations of reads and writes make things look worse > (the writes > slow down the reads). > > > You're of course correct. Hope this satisfies the issue: > > $ cat test.sh > #!/bin/sh > dd if=/dev/zero of=test123456.dat bs=1000000000 count=1 > sync > > $ time ./test.sh > 1+0 records in > 1+0 records out > 1000000000 bytes (1.0 GB) copied, 3.89247 s, 257 MB/s > > real 0m6.158s > user 0m0.001s > sys 0m1.738s > > (obviously dd itself has stuff in RAM. this is why I used time with > sync after the dd. 1GB in 6.158 seconds is 162MB/s.... not too bad. > still better than the Samsung F3 which is one of the fastest disks out > there... same script on that 1TB drive takes 12.239s to complete the > same task..) > > > however, if you feel that the system is very fast after one > year of use > - that's good enough for me. > > > I do. And I don't think it's such a difference. Most writes are pretty > small, and will not halt the system. I think most of the time the > system is slow due to the heads busy with moving around the platter > (seek), something that is almost completely eliminated in SSD - and > *that's* why you have the performance boost. Correct, there are lousy > SSDs that write very slowly, and then block I/O to the lengthy erase > process, and will hang the app or the whole bus (depends on the > controller, I guess?)... but I don't think the X25-E falls under that > category :) > > > do you have the ability to extract wear leveling information > from your > SSD? it would be interesting to know whether the drive is > being used in > a manner that will indeed comply with the life-time expentency > it is > sold with (5 years?), or better, or worse. > > > I don't know, how do you extract such information? > > The rated MTBF of my specific drive is 2 million hours. If I still > know my math, that's some 228 years.... > > -- Shimi
wear leveling has nothing to do with MTBF. once you write ~100,000 times to a single cell in the SSD - it's dead. due to the wear leveling methods of the SSD - this will happen once you write ~100,000 times to all cell groups on the SSD - assuming the wear-leveling algorithm of the SSD is implemented without glitches. note that these writes don't come only from the host - many of them are generated internally by the SSD, due to its wear-leveling algorithms. an SSD could perform several writes for each host-initiated write operation on average. intel claims their X25-E has very impressive algorithms in this regard. it'll be interesting to check these claims with the actual state of your SSD. fetching wear-leveling info is SSD-dependent. you'll need to check if intel provides a tool to do that on linux, for your SSD. --guy _______________________________________________ Linux-il mailing list Linux-il@cs.huji.ac.il http://mailman.cs.huji.ac.il/mailman/listinfo/linux-il
