[dm-devel] mirroring: [patch 1 of 8] device failure tolerance

[Greg Freemyer]

On 6/30/05, Jonathan E Brassow <jbrassow at redhat.com> wrote:
> 
> On Jun 30, 2005, at 10:13 AM, Greg Freemyer wrote:
> 
> > On 6/29/05, Jonathan E Brassow <jbrassow at 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
> 

Sounds like you have more ambitious plans than DRBD.   (They have
active-passive now and IIRC they plan the next major release to have
active-active, but I think only on 2 nodes.)

Is the GFS team planning on supporting this infrastructure.  I hope so.

Greg
-- 
Greg Freemyer
The Norcross Group
Forensics for the 21st Century