Summary: EVA Continuous Access with TruCluster

The original question is at the end of this email.

Continuous access does not provide seamless failover for a TruCluster. All 
worst case failures would require a reboot of the cluster.

Suggestions for DR/HA included:

- Use LSM for everything but CFS root, usr, var and boot partitions.  Clone 
the cluster for quick recovery of the cluster upon EVA failure.

- Script failover to remap the LUNS and reboot

- Look at possible McData (or other vendor) switch options that might 
support some seamless failure.  I haven't done this yet.

- Performance of CA also has been raised as an issue, at least in 
synchronous mode.  I don't know how to quantify this yet.  Our physical 
separation of the EVAs would be only about 2km.


Thanks to:

Jeffrey Hummel
Kelly Graham
Tom Webster
Raul Sossa
Danielle Georgette
Thomas Sjolshagen

--On Wednesday, May 18, 2005 5:06 PM -0400 Todd Acheson <[email protected]> 
wrote:

> Hi,
>
> We had our EVA5K crash for unknown causes about 2 weeks ago and sustained
> 24 hours of downtime.  This raised the issue of how we could build more
> redundancy into our storage stack.
>
> There is Continuous Access (CA), and as I understand it there would not
> be seamless failover.  You would mount the LUNs from the active EVA and
> if that unit failed, you would have to manually remap all filesets to the
> LUNs presented from the backup EVA.
>
> I was pointed to HP MetroClusters as a way to seamlessly have EVA
> failover, but in looking at the HP website, Metroclusters only appear to
> work with HP-UX.  Can anyone validate this??
>
> If CA is indeed only a manual failover for TruClusters then perhaps I
> should just go back to LSM and use it to maintain consistency between 2
> EVAs.  I used to use LSM prior to TruClusters but am a little concerned
> because we have on the order of 20 ADVFS domains with some that are very
> busy.  Not sure if LSM would introduce any performance penalties.
>
> Todd Acheson
> Ohio University
>