Wednesday, February 23, 2011

Partial/No Redundancy on iSCSI Datastores

Expensive fiber SANs are not price-compatible with a lot of my clients, therefore a lot of my time is spent in iSCSI environments.  I’ve noticed in all instances that the Multipathing Status for all my iSCSI datastores are Partial/No Redundancy when viewed on the Storage Views tabs in vCenter.  This bothers me because I always go to great lengths to ensure that I set up my iSCSI multipathing correctly.

I therefore breathed a big sigh of relief when I discovered that this behaviour is a bug as confirmed by VMware Technical Support. The rule for displaying the “Multipathing Status” is as follows:

Full Redundancy – If you have 2 separate adapters and 2 separate paths to the datastore
Partial/No Redundancy – If there is one path which is Up
Unknown – If there is at least one path with an “Unknown” status
All Paths Down – No way to reach the datastore

You will always only have one adapter when using a software iSCSI Initiator, this implies a single point of failure which gives us the dreaded “Partial/No Redundancy” status.  So as things stand now software iSCSI will always be displayed with a degraded status.  Methinks VMWare should develop separate rules / algorithms for fiber and iSCSI SANs…

1 comment:

  1. OMG Thank you! I had a customer asking why the status was like this after an iSCSI implementation. Makes me kick myself now that you explained it.