Date: Tue, 09 Dec 2008 17:40:44 +1100 From: Andrew Snow <andrew@modulus.org> To: Bryan Alves <bryanalves@gmail.com>, freebsd-fs@freebsd.org Subject: Re: ZFS resize disk vdev Message-ID: <493E12EC.4050801@modulus.org> In-Reply-To: <92f477740812082155y3365bec7v5574206dd1a98e26@mail.gmail.com> References: <92f477740812082155y3365bec7v5574206dd1a98e26@mail.gmail.com>
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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. - Andrew
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