On 2006-11-22 at 08:40 +1300, Raj Patel wrote:
At the moment the NetApp is the most familiar to me as I have used one of their NAS boxes before and the simulator provides a pretty good indication of how it works. However the iSCSI seems a bit of a 'bolt-on' and its not clear if it will handle tiered storage as well as the other vendors (then again does it matter?).
The HDS & EMC are unknown quantities (other than what I can glean from the web).
When I looked about a year ago, the EMC Clariions (sp?) didn't directly handle iSCSI; instead, you use a Celerra NAS head which also provides iSCSI. This means that if you provision an iSCSI LUN, it exists as an item in a filesystem which lives in a native LUN dedicated to the NAS unit and the EMC CX box has no separate visibility of it. It's an either/or proposition. Your migration path is to have enough storage to allocate a new native LUN and migrate the data via the clients. This was a CX500, if memory serves.
With the NetApp kit, the NetApp folks were very clear that an iSCSI LUN is visible where you configure it to be visible and if you want to switch from iSCSI to fibre channel then it was a matter of changing the configured interfaces; the LUN remained visible with the same content.
I never really tested the NetApp iSCSI functionality though, but I'm strongly inclined to believe NetApp that this migration works -- it's consistent with what I understand of the design.
-Phil