According to the Unity docs, failover is not supported on the ICS SPEs. Does anyone know why? If Exchange is off-box, why can't we go to SQL 2000 on two SPEs and configure failover?
Pinged the ICS folks about this and here's the official stance on why failover isn't supported on that platform:
Unity Failover is not available for ICS Unity as we have not productized it on an SPE for the ICS-7750. To date, we have had very little customer interest on Unity Failover within the ICS-7750 chassis, but we like to hear from you as you run into opportunities. A few other factors on why ICBU choose not to support Unity Failover;
Added COGS as Unity Failover must utilize SQL2000 rather than MSDE.
6 universal slots within an ICS chassis, 2 Unity blades would burn 2 of them.
Considerable Engineering testing effort would be required & we don't see enough demand to justify it.
Lack of RAID support on the SPE.
FYI, Unity Failover loaded on external severs is supported with the ICS.