Combine several OIDs in a query (NetApp snap reserve)

[arvidjaar]

NetApp may sets aside part of available space on a volume for snapshot keeping (not exactly true but close). This reserved space is represented as separate "volume" in SNMP queries, i.e you get two separate instances like /vol/foo and /vol/foo/.snapshot. So if you graph it you get two graphs for each volume.

The one thing that seems constant is that if index for volume is n then index for virtual snap reserve volume is always n+1

What I'd like is to have single graph per volume that combines both data and snap reserve parts. This would give immediate overview of real space distribution. Unfortunately I am rather at a loss how to do it using queries. Any idea?

TIA