Setting "zfs_arc_max" value in FreeBSD 8.

[Giorgos Keramidas]

On Tue, 19 Jan 2010 14:49:15 +0530, Sherin George <list at sheringeorge.co.cc> wrote:
> Hello,
>
> I am trying to tune ZFS file system by setting "zfs_arc_max" value in
> FreeBSD 8.
>
> In solaris, it is achieved like this
>
> ==============================
> ===================
> For example, if an application needs 5 GBytes of memory on a system with
> 36-GBytes of memory, you could set the arc maximum to 30 GBytes,
> (0x780000000 or 32212254720 bytes). Set the zfs:zfs_arc_max parameter in the
> /etc/system file:
>
> set zfs:zfs_arc_max = 0x780000000
>
> or
>
> set zfs:zfs_arc_max = 32212254720
> =================================================
>
> But, I couldn't find /etc/system file in FreeBSD.
>
> Could some one please guide me to correctly configure "zfs_arc_max" in
> FreeBSD 8.

You have to use /boot/loader.conf in FreeBSD.  Here's a snippet from
mine, for example:

  # Mount the root filesystem from ZFS.
  vfs.root.mountfrom="zfs:kobe/bootfs"

  # ZFS tuning.
  vm.kmem_size="800M"
  vm.kmem_size_max="800M"
  vfs.zfs.arc_max="150M"
  vfs.zfs.vdev.cache.size="15M"
  vfs.zfs.prefetch_disable="1"

  # Autoloaded modules.
  zfs_load="YES"

You can read more about the ZFS support of FreeBSD (including options
like these) at our wiki:

  http://wiki.freebsd.org/ZFS
  http://wiki.freebsd.org/ZFSQuickStartGuide