xfs/kernel gurus,
i am having a problem with a xfs fs on a raid5 array. i experience
extremely poor i/o performance. i notice a LOT of processes enter into
an uninterruptable sleep state when attempting to read/write to the xfs
filesystem.
the system is configured as such:
60GB RAID5 (escalade 7850 + 4x20GB IBM deskstar) mounted on /var
log=internal,bsize=4096,blocks=1839
agcount=58,agsize=262144 blocks
realtime=none
i am mostly a newbie when it comes to raid and xfs, so i do not have
enough experience to diagnose the problem with 100% certainty. baptism
by fire, i should say.
i suspect that my problem is this use of raid5 [0], though i want to
make sure i cover all bases.
i was reading an article on ibm's developerworks website regarding xfs.
this article mentions a few points regarding xfs settings that may cause
the fs to suffer under heavy io load.
the article mentions the following possible bottlenecks:
- lack of an appropriately sized metadata log
- too many allocation groups
could this be the cause of my sleeping i/o-bound processes?
i am extremely annoyed that i cannot yet move/grow the log using
xfs_growfs, so i cannot say that my log is the problem without trashing
the entire filesystem.
looking at kupdated's used cpu time on the box, it's eaten close to
2h30m of time in its four days of uptime, a sharp contrast to the used
cpu time of the kupdate process on the old box (2h over 94 days). this
seems alarming to me, though the old box was running linux-2.2. could
linux-2.4+xfs account for such an increase in kupdate's use of the cpu?
i appreciate any insight/comments/suggestions/information
-mike
[0] raid5 - i'm now wanting to trash the raid5 array and instead create
several mirrored pairs and then use LVM and stripe over the mirrored
pairs. im hoping this will boost performance.
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