Pros / Cons Changing Vdev setup

[fostersimported]

Hi all,

I need to extend my pool, What I am unsure about the pros/cons for each option.

1. Extend each Vdev by adding one HDD to each.

2. Delete the pool and create a RAIDZ2 with 8 HDD

 

[Basil Hendroff]

As I understand it, your pool at present consists of two RAIDZ1 vdevs. I don't believe you can, at present, extend each vdev. What you could do is add another vdev preferably of the same width and type to the pool. However, you now lose a disk per vdev for redundancy.

You may find these resources useful:

• Introduction to ZFS
• Some differences between RAIDZ and mirrors, and why we use mirrors for block storage
• Picking a ZFS Pool Layout to Optimize Performance
• Slideshow explaining VDev, zpool, ZIL and L2ARC for noobs!

 

[Patrick M. Hausen]

Correct. Add three disks for another RAIDZ1 vdev or completely reorganise your pool - losing the data in the process so you need to "park" it somewhere safe.

 

[sretalla]

1. Extend each Vdev by adding one HDD to each.

Can't be done currently, so no pros for now, but in a few years, the pros would be simplicity and space gained for disks added. Retaining IOPS as current.

2. Delete the pool and create a RAIDZ2 with 8 HDD

Better spread of redundancy (can lose any 2 disks with no pool loss), equal loss of capacity to redundancy compared to #1
Con: half the current IOPS.

Option 3 mentioned by others, add 3 disks as an additional RAIDZ1 VDEV
50% more IOPS
Cons: 3 disks lost to redundancy, higher chance of pool loss with 2 disks failing.