md RAID 10 on Linux 2.6.20?

md RAID 10 on Linux 2.6.20?

[thomas62186218]

Hi all,

I am running a home-grown Linux 2.6.20.11 SMP 64-bit build, and I am 
wondering if there is indeed a RAID 10 "personality" defined in md that 
can be implemented using mdadm. If so, is it available in 2.6.20.11, or 
is it in a later kernel version? In the past, to create RAID 10, I 
created RAID 1's and a RAID 0, so an 8 drive RAID 10 would actually 
consist of 5 md devices (four RAID 1's and one RAID 0). But if I could 
just use RAID 10 natively, and simply create one RAID 10, that would of 
course be better both in terms of management and probably performance I 
would guess. Is this possible?

Thanks in advance!

Best regards,
Thomas
________________________________________________________________________
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Re: md RAID 10 on Linux 2.6.20?

[Neil Brown]

On Thursday November 22, thomas62186218@aol.com wrote:
> Hi all,
> 
> I am running a home-grown Linux 2.6.20.11 SMP 64-bit build, and I am 
> wondering if there is indeed a RAID 10 "personality" defined in md that 
> can be implemented using mdadm. If so, is it available in 2.6.20.11, or 
> is it in a later kernel version? In the past, to create RAID 10, I 
> created RAID 1's and a RAID 0, so an 8 drive RAID 10 would actually 
> consist of 5 md devices (four RAID 1's and one RAID 0). But if I could 
> just use RAID 10 natively, and simply create one RAID 10, that would of 
> course be better both in terms of management and probably performance I 
> would guess. Is this possible?

Why don't you try it and see, or check the documentation?

But yes, there is native RAID10 in 2.6.20.

NeilBrown

Re: md RAID 10 on Linux 2.6.20?

[Bill Davidsen]

thomas62186218@aol.com wrote:
> Hi all,
>
> I am running a home-grown Linux 2.6.20.11 SMP 64-bit build, and I am 
> wondering if there is indeed a RAID 10 "personality" defined in md 
> that can be implemented using mdadm. If so, is it available in 
> 2.6.20.11, or is it in a later kernel version? In the past, to create 
> RAID 10, I created RAID 1's and a RAID 0, so an 8 drive RAID 10 would 
> actually consist of 5 md devices (four RAID 1's and one RAID 0). But 
> if I could just use RAID 10 natively, and simply create one RAID 10, 
> that would of course be better both in terms of management and 
> probably performance I would guess. Is this possible?

Yes, and you are correct on the performance. Read the man page section 
on "near" and "far" copies of data carefully, and some back posts to 
this list. Most of us find that using far copies generates slightly 
slower write performance and significantly better read performance.

-- 
bill davidsen <davidsen@tmr.com>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979

Re: md RAID 10 on Linux 2.6.20?

[Peter Grandi]

>>> On Thu, 22 Nov 2007 22:09:27 -0500, thomas62186218@aol.com
>>> said:

> [ ... ] a RAID 10 "personality" defined in md that can be
> implemented using mdadm. If so, is it available in 2.6.20.11,
> [ ... ]

Very good choice about 'raid10' in general. For a single layer
just use '-l raid10'. Run 'man mdadm', the '-l' option and also
the '-p' option for the more exotic variants. Also 'man 4 md'
the "RAID10" section.

The pairs are formed naturally out of the block device list
(first with second listed, and so on).

> 8 drive RAID 10 would actually consist of 5 md devices (four
> RAID 1's and one RAID 0). [ ... ] one RAID 10, that would of
> course be better both in terms of management and probably
> performance I would guess. [ ... ]

Indeed easier in terms of management and there are some
interesting options for layout. Not sure about performance, as
sometimes I have seen strange interactions with the page cache
either way, but usually '-l raid10' is the way to go as you say.