Total Capacity Help

[hardcoded]

Hi all. I have some experience using RAID controls on Linux systems but am new to FreeNAS. This week I installed FreeNAS-11.3-U4.1 on an old spare machine, put three 3TB drives in it and created a storage pool. A couple days later, I added three more 3TB drives, for a total of 6x3TB drives. I used the extend option on the pool to add the additional three, so now I have two RAIDZ1 entries for the six drives.

My question is on the total capacity - FreeNAS shows the data pool as healthy with 3.73 TB used and 6.75 TB available, for a total just over 10 TB. I thought that number should be closer to 15 TiB. Did I go wrong with my math or the configuration? Thanks.

Code:

root@freenas[~]# zpool list -v -H
DataPool        16.2T   5.60T   10.6T   -       -       1%      34%     1.00x  ONLINE   /mnt
        raidz1  8.12T   4.90T   3.23T   -       -       2%      60%
        gptid/72d1e883-f7c3-11ea-b8ec-fcaa14849bcf      -       -       -      -
        gptid/73eaeed3-f7c3-11ea-b8ec-fcaa14849bcf      -       -       -      -
        gptid/73f429fc-f7c3-11ea-b8ec-fcaa14849bcf      -       -       -      -
        raidz1  8.12T   725G    7.42T   -       -       0%      8%
        gptid/b170ccbc-f84f-11ea-aa4e-fcaa14849bcf      -       -       -      -
        gptid/b1e26462-f84f-11ea-aa4e-fcaa14849bcf      -       -       -      -
        gptid/b1e8c08c-f84f-11ea-aa4e-fcaa14849bcf      -       -       -      -
freenas-boot    57G     1.00G   56.0G   -       -       0%      1%      1.00x  ONLINE   -
        da0p2   57G     1.00G   56.0G   -       -       0%      1%

 

[Basil Hendroff]

10.49 TiB to be exact. You will find the ZFS / RAIDZ Capacity Calculator a handy tool.

 

[hardcoded]

10.49 TiB to be exact. You will find the ZFS / RAIDZ Capacity Calculator a handy tool.

Thanks for that Basil. I see that when I calculate by 2 groups, each containing three 3TB drives, I end up with 10.4TiB as you indicated. However, 1 group of 6 drives yields 12.59 TiB. Could I have added the additional three drives to the existing group to increase capacity?

 

[Basil Hendroff]

Could I have added the additional three drives to the existing group to increase capacity?

Unfortunately not. Your pool consists of two virtual devices (vdevs), each a three-disk RAIDZ1 vdev. A current limitation of ZFS is that you cannot add to, or remove disks from, a vdev. You can only grow a pool by adding an additional vdev to it (as you've done) or replacing all the disks in a vdev with larger capacity disks.

If this is a new installation, I suggest you rebuild the pool using a single six-disk RAIDZ2 vdev. Your usable space will remain the same at around 10.4 TiB. The difference is reliability. With your current arrangement, if you lose two disks in one of the RAIDZ1 vdevs, you will lose the entire pool, whereas if you lose two disks in the RAIDZ2 vdev, the pool will continue to function, albeit in a degraded state.

To familiarise yourself with ZFS, I'd encourage you to refer to an Introduction to ZFS by @Ericloewe. It's an excellent resource.