ZFS resize disk vdev

Ivan Voras ivoras at freebsd.org
Tue Dec 9 01:58:39 PST 2008

Andrew Snow wrote:
> Bryan Alves wrote:
>> I'm thinking about using a hardware raid array with ZFS, using a
>> single disk
>> vdev zpool.  I want the ability to add/remove disks to an array, and I'm
>> still unsure of the stability of zfs as a whole.  I'm looking for an easy
>> way to resize and manage disks that are greater than 2 terabytes.
>> If I have a single block device, /dev/da0, on my system that is
>> represented
>> by a zfs disk vdev, and the size of this block device grows (because the
>> underlying hardware raid expands), will zfs correctly expand?  And
>> will it
>> correctly expand in place?
> In theory, this works fine - I have never tried it myself.  The only
> other way to expand a zpool is by adding more vdevs:  You cannot change
> a vdev once it is created other than to take it from a single disk to a
> mirror.
> Sun's ZFS best practice guide states that you should avoid a single disk
> vdev  because performance on the whole suffers and is worse than UFS.
> I am going to publish some benchmark figures soon to back this up, based
> on testing I did with a 16 disk hardware RAID6.  ZFS was *alot* faster
> when I gave it the disks in a RAIDZ2 vdev.

You mean it was a lot faster *per disk*, right? (otherwise, it's
completely expected that a large RAID array will be faster than its

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