I sometimes get asked what the definition of these states is, and I frequently have trouble defining it clearly. Fortunately, EMC’s MirrorView Knowledgebook has been updated to incorporate Release 32, and Appendix A has some succinct definitions. If you can’t be bothered looking them up for yourself, here they are.
- Synchronized – The secondary image is identical to the primary. This state persists only until the next write to the primary image, at which time the image state becomes Consistent.
- Consistent – The secondary image is identical to either the current primary image or to some previous instance of the primary image. This means that the secondary image is available for recovery when you promote it.
- Synchronizing – The software is applying changes to the secondary image to mirror the primary image, but the current contents of the secondary are not known and are not usable for recovery.
- Out-of-Sync – The secondary image requires synchronization with the primary image. The image is unusable for recovery.
- Rolling Back (MV/A only) – A successful promotion occurred where there was an unfinished update to the secondary image. This state persists until the Rollback operation completes.
I think one of the key things here is to pay attention to the various image states, particularly if you’re seeing a lot of out-of sync states on your secondaries. You don’t want to have to explain to people why they can’t recover secondaries in the event of a serious failure. And, more importantly, get on Powerlink and check out the MirrorView Knowledgebook (H2417).