Forgive me if this seems like a fundamental question, but I couldn't really find anything concrete on Google, and I'm not a system administrator by trade.
We are setting up a SAN at our office using NexentaStor with an 8-disk RAID Z3 configuration (8 x 1.36 TB drives) and are in the process of configuring everything.
Right now, in terms of total disk space, we have about 10.8 TB of "real" storage on the SAN, all allocated in a single zpool/zvol. I was considering thin-provisioning the zvol with (say for the sake of argument) 100 TB of space to account for future growth.
It seems simple enough in theory: when we are close to running out of actual disk space, we just add some new drives and it will "just work": no file-system resizing or downtime to worry about.
However, how do we know when we need to add more capacity, short of logging into the SAN every few hours and making sure we still have free space left?
For example, is this normally handled by setting up a
cron job, or does NexentaStor (or ZFS itself) provide warnings when you are near capacity, or is it expected that you should just "know" how much space you have left at any given time and have to keep track of it yourself?
If it helps, the 10.8 TB zvol will be used as backing storage (over iSCSI) for our virtual servers and test virtual machines (which are also thin-provisioned), so part of the problem I see is that it could be easy to run out of disk space if we are constantly creating/snapshotting/restoring VM's (which we do a lot of when testing different machine configurations and software environments).