Feature #1596
open
Allow tuning resilver priority
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Description
Hi all
I recently had an issue with this system. It's got 11 VDEVs with 7 drives each (Hitachi HDS723020BLA642) in RAIDz2, no L2ARC or SLOG. The system lost a drive and just before it was replaced, a rather huge rsync job was started (moving some 27TiB). The drive was replaced Friday afternoon, and Sunday it was still resilvering. The pool has a total of ~100TiB, and 40TiB is in use. After stopping the rsync, the resilver finished in very short time indeed.
So - with the current code, a resilver may take days even on a rather fast system if the system is somewhat loaded. It would be a very nice feature to allow the sysadmin to prioritise resilver over other data traffic, since for some systems, short resilver may be better valued than a more responsive system
roy
Updated by Roy Sigurd Karlsbakk almost 11 years ago
To clarify, zpool said it'll take ~10 hours to finish the resilver while under load. After stopping the rsync, it finished in about 30 minutes...
Updated by Bryan Leaman almost 11 years ago
You can try adjusting zfs_resilver_delay. The default is 2. Decreasing it to 1 or 0 should speed up the resilver at the expense of other I/O. YMMV, but a value of 1 worked well when I was resilvering a disk in a test system recently.
From a discussion thread earlier this year:
6. If the resilver is really slow, it may be due to a reduction in prioritization of the resilver due to other I/O going on:
If there is other work going on, then you might be hitting the resilver
throttle. By default, it will delay 2 clock ticks, if needed. It can be turned
off temporarily using:
echo zfs_resilver_delay/W0t0 | mdb -kw
to return to normal:
echo zfs_resilver_delay/W0t2 | mdb -kw