Freenas and SSD L2ARC

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I thought I’d give FreeNAS a whirl too, see how it goes.  The partitioning commands are a little different, so this post describes what I did for partitioning the SSD.

I read here that the size of the L2ARC should be roughly 4:1 times the size of the level 1 ARC that resides in RAM.  Since I only have a limited amount of ram (currently 10GiB), I decided 50GiB was a good starting point for the size of my L2ARC.  Also I thought I would try creating a log device on the same SSD, although only a 10GiB partition for that.

First of all, we need to find which device the SSD is.  That’s the easy part.

# camcontrol devlist <ATA WDC WD20EFRX-68A 0A80> at scbus0 target 9 lun 0 (da0,pass0) <ATA WDC WD20EFRX-68E 0A80> at scbus0 target 10 lun 0 (da1,pass1) <ATA WDC WD20EFRX-68A 0A80> at scbus0 target 11 lun 0 (da2,pass2) <ATA WDC WD20EFRX-68A 0A80> at scbus0 target 12 lun 0 (da3,pass3) <Fujitsu SSD256GB 5.0.B> at scbus6 target 0 lun 0 (pass4,ada0) <Optiarc DVD RW AD-7700S 1.03> at scbus9 target 0 lun 0 (pass5,cd0) <SMART\000\011 USB-IBM 0000> at scbus10 target 0 lun 0 (pass6,da4)

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# camcontrol devlist <ATA WDC WD20EFRX-68A 0A80> at scbus0 target 9 lun 0 (da0,pass0) <ATA WDC WD20EFRX-68E 0A80> at scbus0 target 10 lun 0 (da1,pass1) <ATA WDC WD20EFRX-68A 0A80> at scbus0 target 11 lun 0 (da2,pass2) <ATA WDC WD20EFRX-68A 0A80> at scbus0 target 12 lun 0 (da3,pass3) <Fujitsu SSD256GB 5.0.B> at scbus6 target 0 lun 0 (pass4,ada0) <Optiarc DVD RW AD-7700S 1.03> at scbus9 target 0 lun 0 (pass5,cd0) <SMART\000\011 USB-IBM 0000> at scbus10 target 0 lun 0 (pass6,da4)

There it is, ada0.  But I’ve already tried creating it as a cache device in the webgui of freenas, so we need to remove the existing partitions first.

# gpart show ada0 => 34 500118125 ada0 GPT (238G) 34 94 - free - (47k) 128 500118024 1 freebsd-zfs (238G) 500118152 7 - free - (3.5k)

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# gpart show ada0 => 34 500118125 ada0 GPT (238G) 34 94 - free - (47k) 128 500118024 1 freebsd-zfs (238G) 500118152 7 - free - (3.5k)

First remove the partition, then the partition table.

# gpart delete -i 1 ada0 ada0p1 deleted # gpart destroy ada0 ada0 destroyed

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# gpart delete -i 1 ada0 ada0p1 deleted # gpart destroy ada0 ada0 destroyed

Now create the 10GiB partition for use with the log device.

# gpart add -t freebsd-zfs -s 10240M ada0 ada0p1 added

1 2	# gpart add -t freebsd-zfs -s 10240M ada0 ada0p1 added

and the partition for l2arc

# gpart add -t freebsd-zfs -s 50G ada0 ada0p2 added

1 2	# gpart add -t freebsd-zfs -s 50G ada0 ada0p2 added

Add it to the zpool

# zpool add bsd_storage cache ada0p2

1	# zpool add bsd_storage cache ada0p2

Finally, check it all looks correct:

# zpool list -v NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT bsd_storage 3.62T 1.90T 1.73T - 45% 52% 1.00x ONLINE /mnt mirror 1.81T 971G 885G - 45% 52% gptid/46bf52cd-5bde-11e4-a01d-10604b929cb8 - - - - - - gptid/4784780a-5bde-11e4-a01d-10604b929cb8 - - - - - - mirror 1.81T 971G 885G - 45% 52% gptid/47f0aa33-5bde-11e4-a01d-10604b929cb8 - - - - - - gptid/485f58f6-5bde-11e4-a01d-10604b929cb8 - - - - - - cache - - - - - - ada0p2 50.0G 45.1G 4.85G - 0% 90%

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# zpool list -v NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT bsd_storage 3.62T 1.90T 1.73T - 45% 52% 1.00x ONLINE /mnt mirror 1.81T 971G 885G - 45% 52% gptid/46bf52cd-5bde-11e4-a01d-10604b929cb8 - - - - - - gptid/4784780a-5bde-11e4-a01d-10604b929cb8 - - - - - - mirror 1.81T 971G 885G - 45% 52% gptid/47f0aa33-5bde-11e4-a01d-10604b929cb8 - - - - - - gptid/485f58f6-5bde-11e4-a01d-10604b929cb8 - - - - - - cache - - - - - - ada0p2 50.0G 45.1G 4.85G - 0% 90%