[Info-vax] RAID 1 across cluster nodes?

[Stephen Hoffman]

On 2019-01-28 16:26:13 +0000, Richard B said:

> I have a 2-node OpenVMS cluster (2x rx2800 i2) which is currently being 
> migrated away from SAN to internal storage.  (Yeah, I know)
> 
> My question is this.  If I wanted to set each drive to RAID 1 could I 
> have one drive on one node and the other drive on the other node?  Or 
> is RAID 1 in this case node specific?

OpenVMS Host Based Volume Shadowing (HBVS) RAID 1 can operate across up 
to six hosts on current OpenVMS releases, and with each RAID-1 member 
volume located on any mix of simple storage controllers or RAID 
hardware controllers.

In this case, you could place three volumes on each of the two hosts.  
Or five and one.  Etc.

Your write I/O will need to be completed across all spindles, so 
there's a downside to adding volumes into a RAID-1 configuration.

If you don't have a shared storage bus available here—SCSI would be the 
low-end choice here, with multi-host-supported parallel SCSI 
controllers and an MSA30-MI box et al—then this configuration is 
inherently a primary-secondary configuration and cannot transparently 
survive the loss of the primary transparently.  Manual intervention is 
always required when the primary fails.

There are folks that use manual fail-overs with hardware RAID and 
external storage and with a cable swap in these configurations, as 
those configurations eliminate the exorbitantly-priced cluster license.



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