Questions about ZFS Tuning

Jamie Paul Griffin jamie at
Mon Sep 17 12:20:17 UTC 2012

[ Volodymyr Kostyrko wrote on Mon 17.Sep'12 at 14:25:09 +0300 ]

> 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.
Yes, I've seen lot's of information about ZFS tunables on FreeBSD which will give me plenty of reading.

I set zfs.zfs.prefetch_disable=0 because some dmesg line suggested/implied it would benefit. I don't recall the exact output now. So, I think it's probably best I just leave things as they are as my system is functioning well enough, as far as I can tell anyway. This is the first time I've used ZFS on FreeBSD so I am still very much in the 'learning process' where that is concerned. 

Thanks for your response Volodymyr. Very much appreciated.

Best wishes, Jamie. 

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