The other day I had a customer purchase a brand new DAE for his VNX.. awesome.. A full shelf of 25 drives. 900 GB SAS drives 2.5″ form factor. Well do some quick math.. you have 5 R5 groups (4+1)
But… what a sec.. What about hot spare? You can run parity and have R5 for protection.. but you still need to be in compliance with your hot spare policy. This customer has the older 3.5″ DAE (15 slots) and the newer drives are 2.5 ” .. what to do..
Will you have a valid hot spare on hand?
After some online research:
Based on the discussion and the reference white papers for both VNX and VNX2 – drive size isn’t of importance. The other factors are: drive type and density. VNX2 is global and won’t take into consideration the drive speed, so you could potentially have slower speed drive of same type for a replacement. This is unknown to the Admin as the policy is set differently.
- Failing drive in-use capacity – The smallest capacity hot spare drive that can accommodate the in-use capacity of the failing drive’s LUNs will be used.
- Hot spare location – Hot spares on the same back-end port as the failing drive are preferred over other like-size hot spares.
- Same Drive type – Hot spare must be of the same drive type.
Bottom line this is good to know because the customer had open slots in their existing 15 slot 3.5 ” DAE and if drive form factor did matter they would need to buy another DAE for the 2.5″ drives!
Here is the Hot Spare drive matrix. It illustrates the Failed drive and compatible spare.