[mythtv-users] Fragmentation On Recording Disk?

Michael MacLeod mikemacleod at gmail.com
Tue Apr 3 21:10:34 UTC 2007

I'd recently been running into performance issues with my combined
frontend/backend. Menu's were slow, hard disk access was slow, and in
general it felt sluggish. When the system was new it did not have these
problems. Recordings and videos are stored on a pair of 250 gig IDE drives,
running in a striped LVM configuration with XFS. They're on different IDE
channels as well, so performance really shouldn't be an issue.

I decided to check the fragmentation on the drive, and xfs_db told me that
it was over 98%. I deleted some recordings that we'd already watched to free
up a bunch of space (114 gigs free space, actually), and ran xfs_fsr in an
infinite loop for a couple of days. I got fragmentation under 3%, and the
system is much improved. I've copied over some new video files and some
shows have been recorded, so fragmentation has increased from that low
again, but is still under 20%. My room mate reports that the system is "3000
percent better." While that's probably a bit of an exaggeration, it is
certainly much more responsive, and the hard disks don't seem to thrash so
much when loading the recordings listing. I've set up a cron script to run
one pass of xfs_fsr each night, so hopefully we can keep the performance
gain for a little while.

root at sixball:~# xfs_db -r /dev/mythtv/mythmedia
xfs_db> frag
actual 3904, ideal 3191, fragmentation factor 18.26%
xfs_db> quit

I just thought I'd share this with the list, and ask if anyone else has
encountered significant performance loss due to disk fragmentation? How
fragmented are your drives?
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