On Mon, Nov 22, 2010 at 6:43 PM, Mikus Grinbergs <mi...@bga.com> wrote: > If "indistinguishable" is true, then there is as much wear to the SD > card from one file-block written as there is from one swap-block > written.
Yes. > I have no measurements whatsoever - but my gut feel is that > the majority of my SD card writes are for file-blocks. If that happens > to be the case, then writes to swap space are a minor wear contributor. Measurements are always helpful. > Also, I'm not familiar with "evil keepout time". But note that on the > new XO-1 F14 build, the "shutdown" time-lapse is only a few seconds. > If actually 30s are needed to keep the SD circuitry happy, perhaps a > delay (and a Release Notes explanation) should be added to the OLPC. This is an issue with particular brands of SD cards. It's not an XO issue, per se. >> To advance the discussion, collecting a quantitative measure >> of "average swap writes per day" given some usage profile would let >> you more-or-less rigorously determine whether swap was 'safe' over the >> 5 year expected lifetime of the device. > > Note: I'm using an external SD card. So if it fails before the OLPC > itself fails, I can at reasonable expense replace this swap device -- I > don't have to plan for a definite wear lifetime. Are you making regular backups? >> If you started >> collecting/recording total data written to your swap partition, I'd be >> very interested to hear (in a month or so) what your numbers were. > > I'm NOT into instrumentation. Please help me in locating software that > will collect the number of swap (and file) writes to a physical device > -- but it must be software that is simple_for_me_to_install_on_OLPC. > [For persistence, the output of that software needs to go to the SD.] The contents of /proc/diskstats seem to contain the interesting info. http://www.linuxquestions.org/questions/suse-novell-60/interpreting-proc-diskstats-360350/ describes their interpretation. A user-friendly script would probably live in /etc/init.d and record the relevant information from /proc/diskstats at shutdown time. --scott -- ( http://cscott.net/ ) _______________________________________________ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel