raid on shared storage

raid on shared storage

[Nils-Henner Krueger]

I'm going to run some kind of cluster using shared
fiber channel disks with linux sw raid on top.

Is it possible to start a raid device on more than one
machine? Is there any write access for example to the
superblock structure when or after starting a raid
device that might crash with a second instance doing
the same?

I'm not talking about mounting file systems in parallel
(btw, how do I detect that a filesystem is already
mounted at a different node, does reiserfs indicate that
somehow?) but simply about starting the md.

Thanks!

nils-henner

Re: raid on shared storage

[Lars Marowsky-Bree]

On 2005-03-18T14:52:02, Nils-Henner Krueger <nhk@netuse.de> wrote:

> I'm going to run some kind of cluster using shared
> fiber channel disks with linux sw raid on top.
> 
> Is it possible to start a raid device on more than one
> machine?

Not yet.

Activating the same md raid on more than one node will destroy your
data, is the gist of it.

RHAT is working on dm-raid1.c to support this, I think. Daniel Philipps
should know more.


Sincerely,
    Lars Marowsky-Brée <lmb@suse.de>

-- 
High Availability & Clustering
SUSE Labs, Research and Development
SUSE LINUX Products GmbH - A Novell Business

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Re: raid on shared storage

[Jure Pe__ar]

On Fri, 18 Mar 2005 14:56:37 +0100
Lars Marowsky-Bree <lmb@suse.de> wrote:

> Activating the same md raid on more than one node will destroy your
> data, is the gist of it.

No. Happened to me multiple times and I still have all the data.

It's not much of a problem if two machines are syncing the same mirror as
long as it is not mounted on any. Once you have the mirror mounted on one of
them, who knows what happens to the write you've just commited.

I don't know what happens on raid5 tho ...

-- 

Jure Pečar
http://jure.pecar.org/
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