We currently have a DELL 2950 with 4 x 400Gb 10krpm SAS drives in RAID 5, and one of those drives has failed. Not having any identical spares (don't slap me, it's not my fault), and not being able to source any identical replacements, we have decided to upgrade the drives to the latest 'standard' sizes and speeds.
Essentially, we are going to purchase 7 x 450Gb 15krpm drives (so that we have a spare), and slowly replace all the existing drives with the new ones.
This is what we have already found out from DELL;
- Replacing a 400Gb with a 450Gb is ok, but only 400Gb will be used
- We can add a disk to the array one at a time, and the controller will expand the array
- Mixing the spindle speeds is ok, they will essentially get averages out
What we do not know is what happens when ALL the drives have been replaced, and are now 450Gb drives, does the RAID controller automatically grow the array to use all 450Gb on each of the disks or will we end up with 50Gb wasted space on each drive?
And if we get 50Gb of wasted space on each drive, will the controller allow us to then create a new RAID 5 array using these 6 x 50Gb spaces and then use that within our OS.
If we can't use the 50Gb, then we don't really care (it's only £100 worth of storage!) but it would be nice to know so that we don't assume that we can use it!