Questions about ZFS Tuning

Jamie Paul Griffin jamie at
Mon Sep 17 10:36:34 UTC 2012


When I installed FreeBSD on my Lenovo Think Center Desktop I created a full ZFS Root file system using Matthew Seaman's excellent article:

My system now is: /home/jamie $ uname -a
FreeBSD 9.1-PRERELEASE FreeBSD 9.1-PRERELEASE #4 r240560: Sun Sep 16 18:40:56 BST 2012     root at  amd64

I've been wondering about ZFS tuning and have read some articles, including the FreeBSD handbook and wiki articles and also some posts in the FreeBSD forum.

The FreeBSD handbook [], section Loader Tunables
suggests adding tunables to /boot/loader.conf for ALL architectures - which I tested:


However, when I rebooted, although it did boot up ok dmesg showed a complaint from ZFS about vm.kmem_size_max being less than 512mb. So I removed it. The only line relating to ZFS tunables in my /boot/loader.conf file is now: vfs.zfs.prefetch_disable=0

To stop this email becoming too long winded, what I'm interested in is are there entries I need/should/recommend to add to /boot/loader.conf to tune ZFS properly and/or Kernel config options I need/should/recommended to add to my custom Kernel.

I have 2GB RAM, and I've set up 2GB GEOM Mirrored Swap. I'm only using one HDD on the machine so it's a fairly basic setup on this machine. Maybe I don't need to do/add anything at all?

Would anyone be kind enough to provide some guidance about this?

Best Wishes, Jamie.

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