[zfs-discuss] Re: Virtualbox VM is unusable on ZFS

Darik Horn dajhorn at vanadac.com
Sun Apr 1 20:54:41 EDT 2012

On Sun, Apr 1, 2012 at 19:28, Vianney Stroebel <vianney at likwid.fr> wrote:
> You're right. I turned off dedup and it's much better. My Win7 guest
> is nearly back to normal speed. Thanks!


> I'm still interested in the "ashift=12" property (for those wondering:
> http://zfsonlinux.org/faq.html#PerformanceConsideration). Is rsyncing
> a zpool to a new one the only way to set this option?


> Is it worth it?

Yes, if the drive has a physical 4k sector size.  Check its datasheet.

> If so, how do I create a second zpool on a whole disk vdev? ("zpool
> create" doesn't seem to work when there's already a zpool).

A whole disk vdev cannot be shared between pools.  Clear and partition
the SSD if you want to split it between two pools.

> Also, what partition size is recommended for ZIL and L2ARC on SSD?

The optimal ZIL size is usually small vice the L2ARC.

Try 1GB for the log and use `zpool iostat -v 10` to watch how much of
it is used while the system is running.  Use the remainder as cache.

Darik Horn <dajhorn at vanadac.com>

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