Re: mirroring: [patch 1 of 8] device failure tolerance

[Jonathan E Brassow <jbrassow@redhat.com>]

On Jun 30, 2005, at 10:13 AM, Greg Freemyer wrote:

> On 6/29/05, Jonathan E Brassow <jbrassow@redhat.com> wrote:
>> This patch defines a couple more states that logs can return, and
>> checks for those states in the mirror code.  The states are useful for
>> logs that have cluster support.
>>
>>   brassow
>
> Have I been asleep?  This is the first I heard of DM having cluster
> mirror support.  I assume the goal is something along the lines of
> what DRBD provides.
>
> Can someone give a very high-level overview of current status, plans,
> etc. related to DM Cluster Mirror support.  And if this related to the
> DRBD project?

Please note that the "mirroring [patch x of 8]..." set for device fault 
tolerance has been replaced with the "mirroring [patch x of 6]..." set.

The cluster mirroring that I'm talking about is active/active and 
capable of handling more than 2 nodes.  It would be used in conjunction 
with a clustered file system - like GFS.  The application sitting on 
the cluster mirror should be cluster-aware.  You wouldn't be able to 
just put ext3 on there and expect it to work in a cluster capacity.

Although there are some minor things that need to happen in the mirror 
proper code (as can be seen from the smallness of the cluster patch), 
the heavy lifting is done by a cluster-aware log.  That is were you are 
keeping track of clean/dirty/recovering state.

An out-dated (but still useful for background) dock can be found at 
http://www.brassow.com/mirroring/index.html

  brassow