I have a question around the Reserve Space setting for each Mount Path under Allocation Policy.
We currently use Netapp storage providing a combination of 20TB and 9TB LUNs to our media agents.
The LUNs are Thick Provisioned and each disk pool maintains a 15% Reserve, so utilization is just under 85% on each disk pool.
In Commvault, each Mount Path also has a Reserve setting of 15% (so 3TB and 1.35TB reserves on each Mount Path).
The Commvault reserve is a legacy setting from a time where the LUNs were Thin provisioned, before being migrated to Thick provisioned LUNs.
I suspect that we are now needlessly 'doubling up' on the amount of Reserve space, however we need to be certain before decreasing the Reserve setting in Commvault.
Support can't seem to provide any kind of 'Best Practice' for what kind of percentage against total size should be used.
I understand that there needs to be enough space in the reserve to close off 'chunks'. Our CommCell has 8GB and 16GB chunk sizes.
Beyond that, is the Reserve used in any other way?
If say, we reduced the Reserve to 7.5% or 5%, would there be any implications for backups and restores, other than us reclaiming a significant amount of space and reducing our overhead?