Zfs pool type

[Koffiejunk91]

Hello,

I want to build a new nas and i'm still figuring out which pool type I want to use. I could buy 3 disks first and configure it as a Z1 array. Then, when needed, upgrade with another 3-disk Z1 array (Stripe over two Z1 arrays).

The other option i'm debating is to build a 4 disk Z2 array and eventually I expand with 2 extra disks.

In order to decide I need to understand what happens when you expand a Z1 or Z2 array.

I've browsed the internet for an answer but I still don't understand.

Lets say i've got that 4 disk Z2 array and expand it with 2 identical disks. Does ZFS integrate the extra storage or is it still the old Z2 array with a "raid0" like stripe to the other disk?

I know ZFS only rearranges the data when it's written again so the old data will stay where it was before the expand.

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[BigDave]

Search Google for "Noobs guide ZFS" select and read top result (it's here on this forum).

 

[Jailer]

If you are planning on adding a few disks at a time and want to maintain adequate redundancy then you could go with mirrors. You will lose half your storage space to parity but it will allow you to safely upgrade your pool over time.

Once you create a vdev it can not have disks added to the vdev to expand it. You can expand your storage pool with additional vdev's. RAIDZ1, RAIDZ2, RAIDZ3, or mirror are examples of a vdev configurations.

Ultimately it's up to you and your risk assessment on how you want to configure your pool.

 

[Koffiejunk91]

If I create a Z1 array consisting of 3 disks and I mirror that array with 3 additional disks I won't be getting any additional storage space. On the other hand two striped Z1 arrays seems a bit risky. I will lose my data if 2 disks in one Z1 array fail...

If I understaand it correctly I won't be able to add 2 disks to an existing Z1,Z2 or Z3 array. The only way to expand an array is swapping disks one at a time right?

 

[BigDave]

zfs RAID and reliability calculator

This handy calculator created by FreeNAS Forum Member @Bidule0hm will help you
to understand basic zfs pool configuration.

If you begin with a three 3TB RAIDz1 pool, the usable space can be increased by two
methods.

• Create a second Vdev by adding a set of three more RAIDz1 disks,

if the disks are of the same size as the first Vdev, the usable space will double (see link to calc above).

• The second method is swapping in larger capacity drives (one at a time) and replace

the original drives until the last drive has been replaced and the pool then auto expands.

The documentation has the directions to perform this method, found here.

 

[Koffiejunk91]

Thanks. I think I'll start with a 3 disk Z1 and expand when needed. I'm not sure if I'll add that second Z1 array to the pool or add a second pool and spread the risks a bit. Either way I will lose 2 disks of space to parity. The PowerPoint in the noobs guide was easier to understand than the PDF. Now I understand vdevs, arrays and pools better (including characteristics).

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