11 votes
Accepted

Offline uncorrectable sectors in SSDs being used for ZFS L2ARC?

Those numbers are obviously bogus. Your SSD doesn't have that many sectors at all, let alone offline uncorrectable ones. Check for firmware updates for your SSD that will fix the problem. Otherwise, ...
Michael Hampton's user avatar
5 votes

zfs: flush cache without exporting

echo 3 > /proc/sys/vm/drop_caches used to clear ZFS cache, but some recent commit changed that to only partially clear it. To restore the old behavior, one has to set the zfs_arc_shrinker_limit ...
shodanshok's user avatar
  • 50.4k
5 votes
Accepted

Is ZFS L2ARC required if primary data is already on SSD?

L2ARC is only useful when using a faster than main pool device, and it is only active when you explicitly attach a cache device to the pool. arc_summary clearly reports your L2ARC stats, but ...
shodanshok's user avatar
  • 50.4k
4 votes
Accepted

ZFS on Linux and KVM: NUMA nodes for host

Manually pinning resources/processes to specific sockets its something that should be only done in very specific circumstances. Moreover, ARC itself is a global resource with (mostly) unpredictable ...
shodanshok's user avatar
  • 50.4k
3 votes

Priming a ZFS L2ARC cache on Solaris 11.3

With a bit of experimentation I've found four possible solutions. With each approach, you need to perform the steps and then continue to read more data to fill up the ZFS ARC cache and to trigger the ...
Tom Shaw's user avatar
  • 3,752
2 votes

Is ZFS L2ARC required if primary data is already on SSD?

To add to @shodanshok's answer: Using an L2ARC with ZFS doesn't unequivocally make things faster. There's a bunch of discussions on various forums where the background is explained in detail, but ...
Mikael H's user avatar
  • 5,089
2 votes

How should I use the new Optum drive?

The ZIL SLOG device is intended for Synchronous write activity. This is used by some databases and also services like NFS. If this is a server where you're running everything on a local ZFS ...
ewwhite's user avatar
  • 198k
1 vote

ZFS l2arc does not warm up

L2ARC is populated only from soon-to-be-evicted ARC buffers. If ARC churn rate is too low, or too high, L2ARC can have issue warming up. To increase L2ARC utilization, you can try to set ...
shodanshok's user avatar
  • 50.4k
1 vote

Cannot re-add cache device to zpool

Try exporting your pool and re-importing it via path or id labels. Then you should be able to remove / add your cache device. For example: zpool export array zpool import array -d /dev/disk/by-path/ ...
shodanshok's user avatar
  • 50.4k
1 vote

In my ZFS box, why is my cache devices leaving a bunch of free space?

Familiarize yourself with arcstat and how ZFS caching works... Something like: arcstat.py -f "time,read,l2read,hit%,hits,miss%,miss,l2hit%,l2miss%,arcsz,c,l2size" 1' This will show the hit rate of ...
ewwhite's user avatar
  • 198k
1 vote

Tracing what blocks go through L2ARC in ZFS on Solaris using dtrace

Turns out that we were using a 2015 version of OpenIndiana and in that particular version the hdr was not set on zio->io_private. This commit from 2016 resolves the issue and by using a 2016 ...
trauzti's user avatar
  • 41

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