Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Hey All, I did some reading and some more tests with this. If you look in the linux kernel documentation linux/Documentation/filesystems/proc.txt it explains the settings for how syncing to disk works in linux. There is a pdflush daemon which wakes up every so often to sync data which is old enough to be synced to disk. How often this wakes up is configurable via /proc/sys/vm/dirty_expire_centisecs and on my system (2.6.10 kernel) defaults to 30 seconds. How old the data needs to be before it is synced to disk is configurable via /proc/sys/vm/dirty_writeback_centisecs and on my system defaults to 5 seconds. This means within 35 seconds of writing data to disk it _will_ be written to disk according to the kernel docs and the setting on my system. This does not happen when using drbd and I think it is may be a problem with the syncing code. I did another test with a drbd partition. In this test I copied the linux kernel onto the drbd partition and then I ran `sync` (which should make pdflush to wake up and flush all data to all disks). I did hear the disk writing after I ran this. I then unplugged the system. After it boots up again I am missing 54 files from that linux kernel I copied, a total of 2k of data. This is with drbd version 0.7.9, linux kernel 2.6.10. This was on a scsi machine Adaptec AIC-7902 controller with dual Opteron 242. Cheers, Scott -- -------------------- Gossamer Threads Inc. ---------------------- Scott Beck Email: scott at gossamer-threads.com Lead Software Developer Phone: (604) 687-5804 http://www.gossamer-threads.com Fax: (604) 687-5806