Had an idea, could someone please tell me why it''s wrong? (I feel like
it has to be).
A RaidZ-2 pool with one missing disk offers the same failure resilience as a
healthy RaidZ1 pool (no data loss when one disk fails). I had initially wanted
to do single parity raidz pool (5disk), but after a recent scare decided raidz2
was the way to go. With the help of a sparse file (''mkfile -n
2000G'') offlined after pool creation, I was able to start using my pool
before my 6th disk arrived. Once it''s here, I''ll swap it in
for the sparse file and let it resilver.
Can someone with a stronger understanding of ZFS tell me why a degraded RaidZ2
(minus one disk) is less efficient than RaidZ1? (Besides the fact that your
pools are always reported as degraded.) I guess the same would apply with
RaidZ2 vs RaidZ3 - 1disk.
Thanks
--
This message posted from opensolaris.org
----- "Peter Tripp" <petertripp at gmail.com> skrev:> Can someone with a stronger understanding of ZFS tell me why a > degraded RaidZ2 (minus one disk) is less efficient than RaidZ1? > (Besides the fact that your pools are always reported as degraded.) I > guess the same would apply with RaidZ2 vs RaidZ3 - 1disk.A degraded raidz2 (minus one disk) will offer the same redundancy as raidz1 would, and the same numbers will apply to raidz3 vs raidz2. One of the good reasons of using raidz2 or even raidz3 is the chance of sector failure during the eventual resilver. Best regards roy -- Roy Sigurd Karlsbakk (+47) 97542685 roy at karlsbakk.net http://blogg.karlsbakk.net/ -- I all pedagogikk er det essensielt at pensum presenteres intelligibelt. Det er et element?rt imperativ for alle pedagoger ? unng? eksessiv anvendelse av idiomer med fremmed opprinnelse. I de fleste tilfeller eksisterer adekvate og relevante synonymer p? norsk.
On Sat, Apr 24, 2010 at 9:21 AM, Peter Tripp <petertripp at gmail.com> wrote:> Can someone with a stronger understanding of ZFS tell me why a degraded > RaidZ2 (minus one disk) is less efficient than RaidZ1? (Besides the fact > that your pools are always reported as degraded.) I guess the same would > apply with RaidZ2 vs RaidZ3 - 1disk. >My understanding of things is along the lines of: A raidz1 vdev writes out data along with 1 parity block. A raidz2 vdev writes out data along with 2 parity blocks. A degraded raidz2 offers the same redundancy level as a healthy raidz1, but it still writes out (or at least calculates) 2 parity blocks. Thus, the degraded raidz2 vdev does more work than a healthy raidz1, even though they both provide the same level of redundancy. -- Freddie Cash fjwcash at gmail.com -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.opensolaris.org/pipermail/zfs-discuss/attachments/20100424/7bd6bf4d/attachment.html>
> From: zfs-discuss-bounces at opensolaris.org [mailto:zfs-discuss- > bounces at opensolaris.org] On Behalf Of Peter Tripp > here, I''ll swap it in for the sparse file and let it resilver. > > Can someone with a stronger understanding of ZFS tell me why a degraded > RaidZ2 (minus one disk) is less efficient than RaidZ1? (Besides the > fact that your pools are always reported as degraded.) I guess the > same would apply with RaidZ2 vs RaidZ3 - 1disk.If a raidz2 is degraded by one disk, then the remaining volume has equivalent redundancy to a healthy raidz1. This is true. However, the double parity calculation and/or storage could possibly perform slower than a healthy raidz1. I don''t know if that''s just an unfounded fear, or if perhaps there''s some reality behind it. Good question. I don''t know the answer.