On 11/26/2010 08:41, Andriy Gapon wrote: > on 26/11/2010 08:05 Adam Vande More said the following: >> As a follow-up, after applying both patches presented in this thread(FreeBSD >> 8.2-PRERELEASE #5: Thu Nov 25 19:14:00 CST 2010), >> >> http://lists.freebsd.org/pipermail/freebsd-stable/2010-November/060298.html >> >> "top -m io" now displays much more info and is generally consistent with >> gstat in that IO spikes occer around the same time. However, gstat and "top >> -m io" are still not displaying any stats for 90%+ of my hard drive >> indicator light blinks. Since the issue effects gstat as well, it doesn't >> seem like it could be related to ZFS. When the system is basically idling, >> the only consistent IO related entries are these; >> >> 6 root 15 0 1 12 0 13 20.00% >> {l2arc_feed_threa} >> 6 root 15 0 1 12 0 13 20.00% >> {arc_reclaim_thre} >> 6 root 15 0 1 12 0 13 20.00% {zvol >> zoot/usr/ho} >> 6 root 15 0 1 12 0 13 20.00% >> {txg_thread_enter} >> 6 root 15 0 1 12 0 13 20.00% >> {txg_thread_enter} >> >> Entries like these occur like clockwork on 30 sec intervals. My theory here >> is that since the ZVOL has UFS + SU, this is causing a sync? >> >> What I'm trying to diagnose is a much more frequent hard drive access which >> occurs on approximately 2 sec intervals. I timed this by pinging localhost >> and comparing the response to the blinks. It's very consistent although not >> completely so as once in awhile the blink occurs every second. If I listen >> carefully I can hear increased drive activity during many of these intervals >> so the indicator light seems to be working correctly. >> >> If anyone has ideas or tests they'd like me to run, it would be appreciated. >> > > Perhaps it's some external component? > E.g. hald is known to perform some disk/media checks every two seconds. >
As well syslod will also cause sync to happen prematurely when something goes to log. syslog.conf(5): *** To ensure that kernel messages are written to disk promptly, syslog.conf calls fsync(2) after writing messages from the kernel. Other messages are not synced explicitly. You may prefix a pathname with the minus sign, ``-'', to forego syncing the specified file after every kernel message. Note that you might lose information if the system crashes immediately following a write attempt. Neverthe- less, using the ``-'' option may improve performance, especially if the kernel is logging many messages. *** This is obviously the old way of ensuring logs are written to disk before crash but now ZFS is handled differently. Check to see if adding '-' to your syslog entries relieves that problem as ZFS will do the right thing to ensure your data is written to disk. -- jhell,v _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"
