Dave,

Can't speak for others - but I've always considered it 'best practice' to divide your disk storage up into several 'Private Volumes'.  Why?  When a non-mirrored spindle in a PV dies, it only takes that PV out with it - allowing the rest of the machine running (unless the PV is the 'mpe_system_volume_set, in which case you're going to be doing a system install).  If it's only one of the data volumes that goes down - the 'system' is still up, greatly facilitating recovery.

If you can't afford arrays that protect the 'system' volume-set, at least you can get something (even if only Mirror/iX for RAID-1) to protect the data volumes.  And if you configure it properly -  RAID-1 is wicked-fast on reads, and pretty decent on writes.

Oh - and to answer your original question:  Yes, A400's can be set up this way.  At least, the ones I administer are setup this way.  The drives 'in the CPU chassis' are setup as "system volume set", and an external mirrored array is the 'data' volume.

Works great.  If the system volume goes down - data isn't likely affected.  If a mirrored drive fails - just swap it for a replacement.  This has gotten my client near 100% up-time for this system, for almost 10yrs now...

Hope this answers at least some of your question(s).

Brian Edminster
Applied Technologies, Inc
"Robust Solutions and Integrations,
   for Today, and Tomorrow"

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