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List:       evms-devel
Subject:    Re: [Evms-devel] dm_multipath + evms + qla2200 device name instability breaking failover/recover
From:       Kevin Corry <kevcorry () us ! ibm ! com>
Date:       2005-05-28 13:06:10
Message-ID: 200505280806.10113.kevcorry () us ! ibm ! com
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Hi Time,

On Fri May 27 2005 6:16 pm, Tim Southerwood wrote:
> Forgive me for posting this to a devel list (in the absence of a users
> list)...

No problem. This is our all-in-one list, dispite the name.

> Been testing the capabilities of a dual attached fiber channel raid unit
> together with linux+evms.
> Any suggestions or obvious things I have missed? All comments welcome,
> including RTFM if you suggest which FM ;-> because I've read everything
> I have find.

Well, my suggestion is...don't use EVMS for the multipath portion of your 
setup. EVMS does come with a plugin that can do multipath, but it was really 
just a temporary solution we put in some time ago. The real future for 
multipath support on Linux is in the newer multipath-tools package, which can 
be found at:

http://christophe.varoqui.free.fr/multipath.html

These tools do detection of the multipath device based on SCSI information 
(instead of needing on-disk metadata like EVMS), set up the devices using 
Device-Mapper, and monitor for path failures and recoveries. I would 
definitely try installing these tools and see if they handle the path 
removal/replacement test better than EVMS. I would also subscribe to dm-devel 
(see http://sources.redhat.com/dm/), where development and testing discussion 
usually takes place.

And if that works for you, you can still use EVMS to do volume management on 
top of the multipath device. When you start EVMS, it should simply see the 
multipath device as a "disk", and you can use it like you would any other 
disk (for partitioning, software raid, lvm, snapshots, etc).

Let me know how that goes, or if you have any other questions about EVMS.

-- 
Kevin Corry
kevcorry@us.ibm.com
http://www.ibm.com/linux/
http://evms.sourceforge.net/


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