On 06/05/2011 10:03, Keld Jørn Simonsen wrote:
On Fri, May 06, 2011 at 01:31:59PM +0600, Roman Mamedov wrote:
On Fri, 6 May 2011 09:17:52 +0200
Keld Jørn Simonsen<keld@xxxxxxxxxx> wrote:
I would like linux MD raid10 functionality to be part of the Linux MD
RAID1 module, and be called raid1. This is in accordance with the
use of the RAID1 term as standadized by SNIA. In fact the RAID10-offset
layout is an implementation of a SNIA RAID specification. The RAID10-near
layout is an implementation of a simple RAID layout. And the RAID10-far
layout is just another layout far a mirrored RAID. So all these types
could just be defined as different RAID1 layouts.
RAID1 is RAID1, RAID10 is RAID10.
RAID1 on 4 drives is very different from RAID10 on 4 drives.
Don't add confusion by trying to rename RAID10 to RAID1.
How are they different?
Say what is the difference between a Linux MD RAID1 with 4 disks, and
the default Linux MD RAID10 with 4 disks? (in the near layout)?
RAID1 is traditionally a mirror only setup (ok, some RAID
implementations may do some load-balancing of some sort). So a RAID1
with 4 disks is one data set copied onto 4 disks. Bandwidth is roughly
the same as a single disk (ignoring any load balancing).
RAID10 is mirror and stripe. A RAID10 with 4 disks is similar to a 2
disk RAID0 (double bandwidth with data split in half across both disks),
but with each disk having a mirror (which brings the total up to 4 drives).
Additionally, a RAID1 disk (at least using MD) can be accessed just like
a normal disk (good for recovery etc.) however a single disk out of a
RAID10 array is next to useless.
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