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Add spa_slop_shift module option

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Allow for easy turning of a pools reserved free space.  Previous
versions of ZFS (v0.6.4 and earlier) held 1/64 of the pools capacity
in reserve.  Commits 3d45fdd and 0c60cc3 increased this to 1/32.
Setting spa_slop_shift=6 will restore the previous default setting.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3724
This commit is contained in:
Brian Behlendorf 2015-09-01 09:45:10 -07:00
parent 3f1cc17c90
commit 6cde64351e
2 changed files with 19 additions and 0 deletions
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16
man/man5/zfs-module-parameters.5
View File

@ -301,6 +301,22 @@ rewind" (\fB-X\fR) pool import.
Default value: 10000
.RE
.sp
.ne 2
.na
\fBspa_slop_shift\fR (int)
.ad
.RS 12n
Normally, we don't allow the last 3.2% (1/(2^spa_slop_shift)) of space
in the pool to be consumed. This ensures that we don't run the pool
completely out of space, due to unaccounted changes (e.g. to the MOS).
It also limits the worst-case time to allocate space. If we have
less than this amount of free space, most ZPL operations (e.g. write,
create) will return ENOSPC.
.sp
Default value: 5
.RE
.sp
.ne 2
.na

3
module/zfs/spa_misc.c
View File

@ -2094,4 +2094,7 @@ MODULE_PARM_DESC(zfs_deadman_enabled, "Enable deadman timer");
module_param(spa_asize_inflation, int, 0644);
MODULE_PARM_DESC(spa_asize_inflation,
"SPA size estimate multiplication factor");
module_param(spa_slop_shift, int, 0644);
MODULE_PARM_DESC(spa_slop_shift, "Reserved free space in pool");
#endif