2012-04-04 03:35 PM
From the v-series maintenance guide
For any given LUN, Data ONTAP will assign one path as the active, and the other path as the
passive/failover path. For tier 1(active-active) arrays, the “active” path will be split as evenly as possible
between available paths for any group of LUNs. For tier 2 arrays (active-passive) the array will tell us which
path is preferred for any given LUN.
I assume this refers to how the backend array is configured? a tier 1 array has both controllers active?
2012-04-09 06:48 AM
When the array LUNs are created, a "host" type is chosen (per the V-Series Implementation Guides in the DataONTAP documentation). This ensures the correct settings (including offsets if needed) are chosen.
Generally speaking, a Tier 1 array will have symmetric paths. In ALUA terms, both paths would be Active/Optimized. These have equal cost, and array LUN access would be evenly split (half the LUNs on one path, the other half on the other path.)
A Tier 2 array may have asymmetric paths. In ALUA terms, one path is Active/Optimized, and the other is Active/Non-Optomized. In this case, all the array LUNs in that group would use the A/O path, and the A/N path would be the failover path
In both cases we depend on the array to tell us which paths are active or preferred.
Hope that helps!
Technical Marketing Engineer
2012-07-04 02:32 PM
Thanks for that, we were trialling an unsupported config with a HDS HUS150 behind a V6280. Dont ask why
One of the things i notices was we weren't able to get it running Active/active even though the HUS supports that kind of I/O my assumption was it was defaulting to active/passive due to it not quite understanding what array was connected to it. Which makes a certain amount of sense.