FreeNAS pool configuration


#1

Hi,

We are setting up an Xcp-ng cluster with 3 nodes and decided to use FreeNAS to provide the shared storage using iSCSI with MPIO as the server has got 2x Intel X520 Dual-Port SFP+ 10Gb Mezz network card installed in it and we will use the classic 1Gb NIC for management.

The server has 6 x 600GB SAS 10k 6Gbps Hard Drives installed and has no room for anymore disks. We would like some help deciding on the desk way to create our pool inside FreeNAS.

We first tough that we would need to create 1x pool containing 3x Vdevs. Each vdev with 2x disk in mirror but we are not sure if this is the best way to create a pool to store VMs.

As we are mainly hosting website and a few other services, we do not expect to need a lot of storage at first. We also have a Dell PowerVault MD1200 we could plug to the FreeNAS server later if required.

Could anyone please advise us on what is the best layout to create the pool for block storage?

Thank you
Any advise is welcome.


#2

Putting them all in one raidz2 would be fine, but for a more in depth answer on ZFS & speed read through this: https://calomel.org/zfs_raid_speed_capacity.html


#3

@LTS_Tom beat me to posting the link by a minute.


#4

This is very interesting. So according to this blog post, I should be using raidz2 because I only have 6 disks. Should I crack on with raidz3 in your opinion?

  • RAIDZ-2 (raid6) used with six(6) disk or more.
  • RAIDZ-3 (raid7) used with eleven(11) disks or more.

#5

It’s 5 AM here in Detroit and I had not had enough coffee. I meant to type raidz2 in my previous post (it’s now corrected)


#6

The way I understand it is, with raidz2, any 2 disks can fail, whereas when you have 3 vdevs with 2 mirrored disks each and 2 disks of the same vdev fail, the vdev (and in extension you storage pool) is completely lost.

Also, you’ll have the capacity of 4 drives with raidz2, while in the mirrored configuration you’ll only have the capacity of 3 drives.