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Diffstat (limited to 'man/man8/zpoolconcepts.8')
| -rw-r--r-- | man/man8/zpoolconcepts.8 | 24 |
1 files changed, 22 insertions, 2 deletions
diff --git a/man/man8/zpoolconcepts.8 b/man/man8/zpoolconcepts.8 index 60845eef2..c2fc34971 100644 --- a/man/man8/zpoolconcepts.8 +++ b/man/man8/zpoolconcepts.8 @@ -323,8 +323,28 @@ If a read error is encountered on a cache device, that read I/O is reissued to the original storage pool device, which might be part of a mirrored or raidz configuration. .Pp -The content of the cache devices is considered volatile, as is the case with -other system caches. +The content of the cache devices is persistent across reboots and restored +asynchronously when importing the pool in L2ARC (persistent L2ARC). +This can be disabled by setting +.Sy l2arc_rebuild_enabled = 0 . +For cache devices smaller than 1GB we do not write the metadata structures +required for rebuilding the L2ARC in order not to waste space. This can be +changed with +.Sy l2arc_rebuild_blocks_min_l2size . +The cache device header (512 bytes) is updated even if no metadata structures +are written. Setting +.Sy l2arc_headroom = 0 +will result in scanning the full-length ARC lists for cacheable content to be +written in L2ARC (persistent ARC). If a cache device is added with +.Nm zpool Cm add +its label and header will be overwritten and its contents are not going to be +restored in L2ARC, even if the device was previously part of the pool. If a +cache device is onlined with +.Nm zpool Cm online +its contents will be restored in L2ARC. This is useful in case of memory pressure +where the contents of the cache device are not fully restored in L2ARC. +The user can off/online the cache device when there is less memory pressure +in order to fully restore its contents to L2ARC. .Ss Pool checkpoint Before starting critical procedures that include destructive actions (e.g .Nm zfs Cm destroy |