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Increase zfs_vdev_async_write_min_active to 2 

Resilver operations frequently cause only a small amount of dirty data
to be written to disk at a time, resulting in the IO scheduler to only
issue 1 write at a time to the resilvering disk. When it is rotational
media the drive will often travel past the next sector to be written
before receiving a write command from ZFS, significantly delaying the
write of the next sector.

Raise zfs_vdev_async_write_min_active so that drives are kept fed
during resilvering.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: DHE <git@dehacked.net>
Issue #4825
Closes #5926
This commit is contained in:
DHE 2017-03-25 22:36:28 -04:00 committed by Tony Hutter
parent 94d353a0bf
commit 5e6057b574
2 changed files with 7 additions and 2 deletions
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7
man/man5/zfs-module-parameters.5
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@ -883,7 +883,12 @@ Default value: \fB10\fR.
Minimum asynchronous write I/Os active to each device.
See the section "ZFS I/O SCHEDULER".
.sp
Default value: \fB1\fR.
Lower values are associated with better latency on rotational media but poorer
resilver performance. The default value of 2 was chosen as a compromise. A
value of 3 has been shown to improve resilver performance further at a cost of
further increasing latency.
.sp
Default value: \fB2\fR.
.RE
.sp

2
module/zfs/vdev_queue.c
View File

@ -146,7 +146,7 @@ uint32_t zfs_vdev_sync_write_min_active = 10;
uint32_t zfs_vdev_sync_write_max_active = 10;
uint32_t zfs_vdev_async_read_min_active = 1;
uint32_t zfs_vdev_async_read_max_active = 3;
uint32_t zfs_vdev_async_write_min_active = 1;
uint32_t zfs_vdev_async_write_min_active = 2;
uint32_t zfs_vdev_async_write_max_active = 10;
uint32_t zfs_vdev_scrub_min_active = 1;
uint32_t zfs_vdev_scrub_max_active = 2;