zpool design question

[nikkon]

Hi all,

After defining the HW to use I have a question related to zpool design.
Will use for this setup: 4x 4TB wd red & from the old NAS 4x 2TB Seagate green.
By definition, a pool is made up of one or more vdevs, which themselves can be a single disk or a group of disks. Based on this statement is it recommended to have a setup like this:

zpool1= RAIDZ0 containing 2x 2TB old Seagate drives
zpool2= RAIDZ2 containing 4x 4TB red + zpool1
zpool3= mirror

Concerns:
- mixing different drives will affect performance?
- old ones can die faster
- the main goal is to get RAIDZ2 for the main zpool
- can zpool1 be used only for parity?

thank you

 

[SweetAndLow]

I would make a pool with 2vdevs both in raidz2 or just use mirrors so you can add drives in pairs.

Sent from my Nexus 5X using Tapatalk

 

[Robert Trevellyan]

zpool1= RAIDZ0 containing 2x 2TB old Seagate drives
zpool2= RAIDZ2 containing 4x 4TB red + zpool1

This is not a valid structure.

can zpool1 be used only for parity?

No. It looks like you've tried to do your homework, based on how you defined pools and vdevs, but something got lost in translation. Perhaps it will help to note that redundancy is created at the vdev level, not the pool level. This means your vdevs are stripes, mirrors, RAIDZ1, RAIDZ2 or RAIDZ3. You then assemble a pool from vdevs, ideally all with the same geometry, but you can get away with mixing and matching if you insist.

 

[nikkon]

I see. thx for the observation. makes sense now. will do a test using a VM and see how I can do this config.
the reason for this mix is RAIDZ2 only.
how much will this mix impact performance? disks have almost the same rpm, maybe different cache sizes.

 

[SweetAndLow]

More vdevs will improve iops which will help with performance. I like this layout better than when people make multiple pools, I don't agree with the reasons for multiple pools.

The different disk speeds will affect things but probably not noticeable and hard to measure.

I would just make sure to fully burn in the new and old drives to verify they don't fail on you.