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? -- ==========================================================Peter C. Lai | Bard College at Simon's Rock Systems Administrator | 84 Alford Rd. Information Technology Svcs. | Gt. Barrington, MA 01230 USA peter AT simons-rock.edu | (413) 528-7428 ===========================================================
http://blogs.sun.com/ahl/entry/double_parity_raid_z Looks like raidz2 is recommended for better protection against failures than 2 stripes. On Tue, Feb 16, 2010 at 2:47 PM, 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? > -- > ==========================================================> Peter C. Lai | Bard College at Simon's Rock > Systems Administrator | 84 Alford Rd. > Information Technology Svcs. | Gt. Barrington, MA 01230 USA > peter AT simons-rock.edu | (413) 528-7428 > ==========================================================> > _______________________________________________ > freebsd-stable@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscribe@freebsd.org" >-- Joshua Boyd JBipNet E-mail: boydjd@jbip.net http://www.jbip.net
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