Date: Tue, 16 Feb 2010 12:24:21 -0800 From: Freddie Cash <fjwcash@gmail.com> To: freebsd-stable@freebsd.org Subject: Re: raidz/2 stripe widths Message-ID: <b269bc571002161224o2d2ef9f3s942cfd7d0b7407d0@mail.gmail.com> In-Reply-To: <20100216194707.GQ4648@cesium.hyperfine.info> References: <20100216194707.GQ4648@cesium.hyperfine.info>
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On Tue, Feb 16, 2010 at 11:47 AM, Peter C. Lai <peter@simons-rock.edu>wrote: > Which one might be "better" on pool that will consist of 6 disks: > > 6x raidz2 > or > 2 stripes of 3 disks in raidz? > > It should provide slightly less reliability (still allows for 2 disks to be > off the array at a time) but the latter should improve reads since a given > read only has to touch 3 spindles at a time instead of 5? > Depends. Do you want better reliability/redundancy (raidz2) or more throughput/IOPS (2x raidz1)? The max IOPS of a raidz vdev will be that of 1 disk. Thus, to get better IOPS, you have to have multiple raidz vdevs. The overly-simplistic way to look at is to think of the entire raidz vdev as a "single disk". Then it's an easy comparison: 1 disk is slower than 2 disks striped together. -- Freddie Cash fjwcash@gmail.com
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