From: Mike Tran <mhtran@us.ibm.com>
To: linux-raid@vger.kernel.org
Subject: Re: EVMS or md?
Date: Mon, 04 Apr 2005 14:28:48 -0500 [thread overview]
Message-ID: <1112642928.25469.28.camel@dyn95395156> (raw)
In-Reply-To: <200504040708.j3478bm03863@www.watkins-home.com>
Hi Guy,
On Mon, 2005-04-04 at 02:08, Guy wrote:
> I am top posting since I am starting a new topic.
>
> Don't get me wrong, I like and trust md, at least with kernel 2.4.
>
> This is the first I knew about EVMS, the website makes it sound wonderfull!
> http://evms.sourceforge.net/
>
> Is EVMS "better" than md?
> Is EVMS replacing md?
> Any performance data comparing the 2?
EVMS uses MD and Device Mapper (DM). So, EVMS does not replace MD. For
RAID-1 & RAID-5, EVMS ioctl md driver to start the array. For MD's
RAID-0 and LINEAR arrays, EVMS uses DM stripe and linear targets to
create device nodes.
You can say EVMS replaces mdadm (sorry, NeilB :))
Regarding performance issue (raid1 & raid5), I/O requests from MD will
appear on DM's queue. So, it is probably slower. How much slower, we
never run any benchmark to find out.
>
> One bad point for EVMS, no RAID6. :(
We (EVMS team) intended to support RAID6 last year. But as we all
remember RAID6 was not stable then. I may write a plugin to support
RAID6 soon.
> One good point for EVMS, bad Block Relocation (but only on writes).
> Not sure how EVMS handles read errors.
As I mentioned above, kernel MD driver handle I/O requests for raid1 and
raid5.
>
> I am getting on the mailing list(s). I must know more about this!!!
>
Welcome aboard :)
--
Regards,
Mike T.
next prev parent reply other threads:[~2005-04-04 19:28 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-04-04 2:52 raidreconf / growing raid 5 doesn't seem to work anymore Mike Hardy
2005-04-04 5:48 ` David Greaves
2005-04-04 7:08 ` EVMS or md? Guy
2005-04-04 7:57 ` David Greaves
2005-04-04 19:28 ` Mike Tran [this message]
2005-04-04 21:46 ` David Kewley
2005-04-04 22:15 ` H. Peter Anvin
2005-04-04 22:52 ` Gordon Henderson
2005-04-04 23:03 ` Mike Tran
2005-04-05 6:17 ` Brad Campbell
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