> Assuming OLPC isn't using TRIM support on the SD cards, writes to the > swap space are indistinguishable from writes to any other space on the > card. That means that writes to the swap "partition" could potentially > corrupt other data on the card, especially if it occurs less than 30s > before removal of power (or whatever that evil keepout time is).
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. 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. 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. > 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. > 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.] mikus _______________________________________________ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel