Questions about ZFS Tuning

Volodymyr Kostyrko c.kworr at
Mon Sep 17 11:25:15 UTC 2012

17.09.2012 13:36, Jamie Paul Griffin wrote:
> 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:

Handbook is old and cripsy about that all thing yet provides a useful 
link to

  - you don't need kmem_size/arc tuning on amd64 generally;
  - zfs.zfs.prefetch_disable=0 will cause system eat more RAM then 
without it;
  - there are a lot of tunables but you should learn what you are doing 
before setting anything, for example changing recordsize for already 
running MySQL database filesystem will do nothing at all.

Sphinx of black quartz judge my vow.

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