Pool Occupancy Query

[tlauwk]

Hi,

Forgive the noobie question but just wanted to confirm my understanding of pool occupancy after reading various posts here. For context, I'm about to install Truenas Core onto a Dell R730xd for ESXi (8.0) virtual machine storage using iSCSI.

Dell R730xd:

• 2x SAS HDD 300GB (for Truenas O/S)
• 12x SAS HDD 8TB (for storage)
• Dell PERC H330 (to be flashed to Dell HBA330 IT Mode)
• 128GB RAM

For performance reasons, I'm supposed to keep my pool occupancy as low as possible. Lets say 50% occupancy for argument's sake so the math will be easier to present.

I'll create the following:

• a pool consisting of 2-way mirrored vdevs (x6) so total pool size is 48TB (using up all 12 storage disks)
• a zvol size of 48TB
• map the zvol to ESXi and create the VM datastore

And I make sure the VM datastore never exceeds 50% utilization (or 24TB usage ... VMs are all thin provisioned).

Is this how a pool occupancy usage of 50% is calculated?

Thanks.

 

[Ericloewe]

• 2x SAS HDD 300GB (for Truenas O/S)
• 12x SAS HDD 8TB (for storage)

Are those disks lying around? Because if they're not, going with SAS is just a waste of money in 99% of cases.

a pool consisting of 2-way mirrored vdevs (x6) so total pool size is 48TB (using up all 12 storage disks)

More like 43,6 TB.

a zvol size of 48TB

And I make sure the VM datastore never exceeds 50% utilization (or 24TB usage ... VMs are all thin provisioned).

Why not just make the zvol 24ish TB? That way you get a decent estimate of how much space is really available, given the 50% target, on the client's side.

 

[tlauwk]

Are those disks lying around? Because if they're not, going with SAS is just a waste of money in 99% of cases.

More like 43,6 TB.


Why not just make the zvol 24ish TB? That way you get a decent estimate of how much space is really available, given the 50% target, on the client's side.

Yes, the disks are already available as its a decommissioned server that I'm re-purposing for Truenas.

Ah OK, so the zvol can be 50% of the pool. Thanks for the help, much appreciated.