May 19, 2015

Hand-on - EMC VNX2 - Hot Spare Policy

Hot Spare Policy in Unisphere. 
Because any suitable unbound drive can now be used as a permanent spare, Hot Spare Policies are used to monitor the number of unbound drives. This is intended to prevent unwanted situations where no hot spares are unintentionally left on the array.

1. Hover over System
2. Click Hot Spare Policy





Note the Recommended Hot Spare Policy is 1 per 30 disks.
Click NL SAS. The Hot Spare Policy for the NL SAS drives has already been changed to No Hot Spares.
Note that this does not mean there will be no hot spares for NL SAS drives. Any unbound drive will still be used as a hot spare in the event of a drive failure. No Hot Spares only means the Hot Spare Policy will not reserve any drives to be a hot spare and you will not be warned if all of the drives are bound






Change the Policy


Change the Policy - 1 per 10
After doing this, you see that the number of disks to keep unused changes to 2 disks. This is because you set the policy to keep 1 out of every 5 drives as a hot spare. Since you have 10 SAS Flash drives total, the policy reserves 2 drives.
Even though Joe wants to have enough hot spares to be extra safe when the new drives arrive, keeping 1 out of every 5 drives for a hot spare is wasting a lot of drives. You decide to change the policy to 1 per 10 instead. Use the drop down menu to change the policy to 1 per 10.




Apply Changes
Notice that the number of disks to keep unused changes to 1 disks. This number will increase depending on how many drives Joe ordered to be added to the system. If even 1 new drive is added, the number to reserve for hot spares will increase to 2, which meets Joe's requirement of having at least 2 spare Flash drives available at any time.




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