Hello
I have a server with Truenas Scale with 30x3TB HDD and 30x2TB HDD.
What configuration do you recommend for the pools? A single pool or two?
I had thought about: pool1: 6 x RAIDZ1 | 5 wide | 3TB
pool2: 6 x RAIDZ1 | 5 wide | 2TB
The purpose is file archiving.
Thank you
The general maximum for RAID-Zx vDevs is 12. You would get better redundancy for archiving with 3 x 10 disk RAID-Z2 instead of 6 x 5 disk RAID-Z1. Though with 1/2 as many vDevs their is an IOPS reduction. Nothing serious, especially nothing for archival data.
The math for number of disks used for redundancy works out the same:
But with RAID-Z2 you get better redundancy if you ever want to replace your 2TB or 3TB disks. (Of course you have to replace more disks with wider RAID-Zx vDevs to get the vDev to grow in size…)
It is perfectly fine to mix 2TB RAID-Zx vDevs with 3TB RAID-Zx vDevs in a single pool. ZFS will favor writing to the larger 3TB disk RAID-Zx vDevs until all vDevs have equal amount of free space.
However, it is up to you to decide if a ZFS pool of 30 disks is your limit. Or 60 disks. Loss of a single vDev means loss of the entire pool. Thus, the desire to increase redundancy per vDev.
Seriously, my first advice would be to get larger drives, but (much!) less of them.
And raidz2.
Unless there are different kinds of archives, there’s no reason to make multiple pools. Except you can’t remove raidz# vdevs; if you intend to replace the puny disks with larger ones later on, you could make one pool per disk shelf so you could expand the capacity of one shelf by replacing disks, replicate the data from another shelf/pool there and then discard the other shelf—and reduce the number of disks.
You do not say how old these drives are, but given the size I am assuming they are reasonably old and therefore reasonably likely to fail.
A single pool makes space management much easier - the important thing is to make sure that it is so redundant that you won’t lose a vDev.
My own personal choice, 1 pool, multiple vdevs but with 10% spare drives and using DRAID because it resilvers quicker:
Hello
First of all, thank you for your response.
This configuration gives me a warning:
“Recommended number of data disks for optimal space allocation should be power of 2 (2, 4, 8, 16…).”
The documentation says “multiples of 2”, not even “power of 2”. Another annoying discrepancy in TrueNAS?
Data Devices Data stripe width for the VDEV. Select the number of disks from the options provided on the dropdown list. TrueNAS recommends that dRAID layouts have data devices allocated in multiples of 2.
That is for dRAID, a different type of vDev than RAID-Zx.
While dRAID can be interesting, for practical sake, if you don’t know what dRAID is, you probably don’t need it. Use RAID-Zx instead.
