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Date: Tue, 17 Apr 2012 16:56:34 +0400
From: Slawa Olhovchenkov <slw@zxy.spb.ru>
To: carlopmart <carlopmart@gmail.com>
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Subject: Re: ZFS options for FreeBSD 8.3
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On Mon, Apr 16, 2012 at 06:57:45PM +0200, carlopmart wrote:

>   I have installed FreeBSD 8.3 amd64 release in an ESXi server. Due to 
> some limitations, I can only assign 2GiB of RAM to this virtual machine 
> and I need to use ZFS as filesystem to store some data (MySQL databases).
> 
>   According to http://wiki.freebsd.org/ZFSTuningGuide I have configured 
> some options:
> 
> vfs.zfs.write_limit_override=268435456
> kern.maxvnodes=250000
> 
>   According to ZFS version, FreeBSD 8,3 comes with version 28, and 
> reading previous guide there is not need to adjust nothing more.

I am boot 9.0 inside ESXi with 256MB RAM.
And pass buildworld.

/boot/loader.conf:

vm.kmem_size="512M"
vfs.zfs.txg.timeout="5"
vfs.zfs.vdev.cache.size="4M"
vfs.zfs.arc_max="16M"

>   But what about l2arc options?? Do I need to adjust vfs.zfs.arc_max and 
> vm.kmem_size options?? How can I calculate these values??

vm.kmem_size must be >512M. kernel don't allow to setup vm.kmem_size
to more the 2*RAM.

zfs don't allow to setup vfs.zfs.arc_max < max(RAM/32, 16MB).