FreeNAS Single SSD as ZIL and L2ARC

Quick Story I remember I set this up on my FreeNAS server in hopes to get better performance, in reality, I don’t think it helped anything cause of my FreeNAS servers setup. Which was an old desktop with 3 Gigs of memory and a couple SATA drives, 2 spindle and 1 SSD.

Took me a while but I finally found the original source I followed.

Main Parts (assume SSD is ada0):

root@freenas1:~ % gpart create -s gpt ada0
ada0 created
root@freenas1:~ % gpart add -a 4k -b 128 -t freebsd-zfs -s 10G ada0
ada0p1 added
root@freenas1:~ % gpart add -a 4k -t freebsd-zfs ada0
ada0p2 added

List Disk to get GUIDs

root@freenas1:~ % gpart list

Add partitions as Zil and L2ARC on a logical disk (volume0)

root@freenas1:~ % zpool add volume0 log gptid/94a4bd28-aeb7-11e5-99ac-bc5ff42c6cb2
root@freenas1:~ % zpool add volume0 cache gptid/9a79622f-aeb7-11e5-99ac-bc5ff42c6cb2

Nice you can use the zpool command to verify their used as such:

If you are paying attention you’ll noticed the guid are different. Anyway you can use the GUI to see the results as well, if you click the main volume under Storage -> Volume, Then click the Show details button.

If you pick any of the partitions in this list, at the bottom you get a button labeled “Remove”. To undo the previous additions made via the back end SSH.

After this I removed the old Volume completely, including the old File based extent I was using on it.

I then created all new Volumes, one volume on each drive, then created 1 zVol on each volume, then used those zVols as Device based Extents on the iSCSI service…. and I couldn’t believe the performance increase, I couldn’t saturate the 1gbps link before with storage vMotions. Now every single Datastore maxes out the NIC and I hot 100 MB/s plus on every storage vMotion and I increased my storage capacity. W00t (of course I never had storage redundancy to begin with so nothing lost, all gains.

Summary

Don’t bother using a SSD to try and gain speeds on simple homelab FreeNAS servers. It’s useless… “Some more specifics: as a rule of thumb L2ARC is only really useful if you have lots of RAM (64GB+) and a ZIL is only useful if you’re performing lots of synchronous writes.” – anodos

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