From: Gilad Arnold <arnold@cs.berkeley.edu>
To: Drew <drew.kay@gmail.com>
Cc: linux-raid@vger.kernel.org
Subject: Re: migrating from RAID5 to RAID10
Date: Thu, 10 Jun 2010 15:26:26 -0700 [thread overview]
Message-ID: <20100610222625.GA14165@libra.CS.Berkeley.EDU> (raw)
In-Reply-To: <AANLkTim3vrtAfgzY87IAmP6mY9PNiYiQZ1LyuqWHisiD@mail.gmail.com>
On Thu, Jun 10, 2010 at 03:11:43PM -0700, Drew wrote:
> Actually No. If it is RAID-5 as you claim, then currently it is
> effectively a RAID-0.
>
> RAID-5 is Striping with Distributed Parity and requires a *minimum* of
> 3 disks. Two disks, regardless of how you got there, is considered
> a degraded state.
Sounds to me that you can still stripe and distribute parity with two
drives, only that parity will amount to mirroring, and it can still
tolerate a single drive failure. I got there in the usual way, creating
a RAID5 with --raid-devices=2.
--8<------8<------8<------8<------8<------8<------8<------8<------8<----
$ mdadm --detail /dev/md4
/dev/md4:
Version : 0.90
Creation Time : Thu Nov 27 15:48:58 2008
Raid Level : raid5
Array Size : 484391808 (461.95 GiB 496.02 GB)
Used Dev Size : 484391808 (461.95 GiB 496.02 GB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 4
Persistence : Superblock is persistent
Update Time : Thu Jun 10 15:16:45 2010
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 64K
UUID : 1da37f10:3c14071d:40784aba:8675d418
Events : 0.94324
Number Major Minor RaidDevice State
0 8 4 0 active sync /dev/sda4
1 8 20 1 active sync /dev/sdb4
--8<------8<------8<------8<------8<------8<------8<------8<------8<----
Gilad
next prev parent reply other threads:[~2010-06-10 22:26 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-09 15:11 migrating from RAID5 to RAID10 Gilad Arnold
2010-06-10 18:52 ` Roman Mamedov
2010-06-10 19:58 ` Gilad Arnold
2010-06-10 22:11 ` Drew
2010-06-10 22:21 ` Drew
2010-06-10 22:30 ` Gilad Arnold
2010-06-10 22:26 ` Gilad Arnold [this message]
2010-06-16 15:54 ` Bill Davidsen
2010-06-16 18:30 ` Gilad Arnold
2010-06-16 20:15 ` Gilad Arnold
2010-06-17 1:59 ` Bill Davidsen
2010-06-16 21:26 ` Neil Brown
2010-06-17 17:44 ` Gilad Arnold
2010-06-17 22:30 ` Neil Brown
2010-06-18 8:40 ` Keld Simonsen
2010-06-21 22:09 ` Neil Brown
2010-06-17 22:46 ` Gilad Arnold
2010-06-18 2:39 ` Neil Brown
2010-06-18 4:01 ` Gilad Arnold
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