Level of Indirection .. short answer.. anyone?

[Nicodemus]

Ok.. so I have read the SAN Config Guide.. and it says "If you're used to working with traditional SANs, the levels of indirection can initially be confusing." ..no kidding.. I have read and re-read that page a few times... still no idea how they define Levels of Indirection..

Can someone please give me the short understandable answer?

Thanks, - Nicodemus

[rossb2b]

Not direct. Indirection provides a way of accessing instructions, routines and objects when their physical location is constantly changing. The initial routine points to some place, and, using hardware and/or software, that place points to some other place. There can be multiple levels of indirection. For example, point to A, which points to B, which points to C.

In terms of VMware and the virtual machine. You are not accessing the SAN as you would with a Physical Machine. The VM sees the SAN storage because the ESX server sees the SAN storage and is providing an indirect path to your virtual disks.

Does that help?

[Nicodemus]

Yes.. that does help somewhat... Can you tell me why the levels of indirection is related to the SCSI Controller configuration example? Specifically how they intend it for this SCSI Bus Sharing...Virtual and Physical?

It seems it has something to do with Microsoft Cluster Server like cluster in a box or between boxes...?

TIA, - Nicodemus

[rossb2b]

Sure,

With SCSI Bus Sharing you have three options.

1. None

2. Virtual

3. Physical.

Virtual mode can be used when creating a MS cluster of VMs on one physical ESX host.

Physical is used when creating a MS cluster of VMs across two different phycial ESX hosts or clustering a physical box and a VM together.