[zfs-discuss] Virtualbox VM is unusable on ZFS

Steven Anderson hikenboot at yahoo.com
Sun Apr 1 17:52:13 EDT 2012

ashift=12 is that to fix offset of the partitions on the disks?
I have noticed in the past problems where the starting point for the partitions dont line up with windows and layout of the file systems starting at missmatched blocks and block size but I dont really know how to fix the problem with zfs..
--- On Sun, 4/1/12, Vianney Stroebel <vianney at likwid.fr> wrote:

From: Vianney Stroebel <vianney at likwid.fr>
Subject: [zfs-discuss] Virtualbox VM is unusable on ZFS
To: "zfs-discuss" <zfs-discuss at zfsonlinux.org>
Date: Sunday, April 1, 2012, 2:46 PM


I'm using ZFS on Linux ( from the Stable
on Kubuntu 11.10.

Since I moved my VirtualBox Windows 7 VM files to my ZFS disk, it is
unusable : it takes ages to boot and any application takes several
minutes to load or to perform any action that involves disk access.
Host swap goes up about 1 Gb. The same VM was running perfectly on an
Ext4 partition on the same disk.

My Ubuntu guests are not as slow as the Win7 but still much slower in
ZFS than in Ext4.

The host is my laptop, a fairly recent Asus N73SV with 6 Gb RAM.

Dedup is ON on the VM filesystem. Compression was set on lzjb, but
only after the data was copied to the zpool (which means it's not
useful at the moment).

My zpool was created without the "ashift=12" option. If necessary, I'd
be willing to change this, but I'd need someone to tell me how to do
it :-) (import/export does not allow changing this property).

I'm not using ZIL nor L2ARC but I have an SSD in my laptop which I
could use for these if you think I would help. In this case, how large
should they be?


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