[Dovecot] Highly Performance and Availability

[Stan Hoeppner]

Ed W put forth on 2/22/2010 7:03 AM:

> Can you tell me exactly what "Consolidated Backup" means with respect to
> ESX please?  From the brief description on the website I'm not quite
> sure how it varies to say backing up the raw storage using some kind of
> snapshot method?

Here's a decent write up Ed that should answer your questions:
http://www.petri.co.il/virtual-vmware-consolidated-backup-vcb.htm

> I was giving this some thought - essentially the whole problem comes
> down to either some kind of filesharing system which offers up
> individual files, or some kind of block level sharing and you have to
> then run your own filesystem over the block device.

The best solution for this currently existing on this blue planet is SGI's
CXFS.  It is the clustered version of XFS, sharing an identical on-disk
format.  It is the highest performance and most reliable parallel/cluster
filesystem available.  It was initially released simultaneously with XFS in
1994.  It is a clustered file system requiring FC SAN storage.  One host
acts as a CXFS metadata server.  All hosts in the cluster directly access
the same LUN on the disk array controller.  The metadata server coordinates
the notification of blocks that are locked for write access by a particular
node.  The performance is greater than GFS and similar parallel filesystems
due to the centralized metadata server reducing chatter and message latency,
and the fact that the on-disk filesystem is XFS, which as we've discussed is
the fastest filesystem available (aggregate across multiple benchmarks).
Unfortunately, SGI did not open source CXFS, only XFS.  CXFS must still be
licensed from SGI.  I do not know the cost.  For many environments, the cost
is irrelevant, as there simply is no other solution to meet their needs.
For something like clustering IMAP server data for redundancy, CXFS is
probably overkill.  GFS2 should be fine for clustered IMAP storage.

-- 
Stan