Mixing 4TB disks and a 3TB disk: what is the best option?

[ciacnorris]

Hello, I'm preparing to set up my first TrueNAS Community system on an old N36L Microserver with 8GB RAM.

I have an old 3TB disk that I would like to use, and I can buy a couple of 4TB disks (their cost is more or less the same of the 3TB disks so they are the sweet spot on a price/space point of view).

The first option that comes to my mind is to use 3TB on each disk to creat a RAIDZ1, then use the remaining 1TB on the two 4TB hard drives to create a 1TB mirror. Is this configuration possible?

I have set up a TrueNAS installation in Virtualbox to test it but the system isn't allowing me to mix disks of different sizes in a pool. I'm a total noob so I don't understand if I'm missing some steps or this is just not possible.

If what I want to do is impossible, what would you suggest me, provided that I already have a 3TB drive, that I could buy 4TB drives and that the N36L has a total space for 4 drives (or 5, if I use a USB stick for the operating system)?

 

[jgreco]

The first option that comes to my mind is to use 3TB on each disk to creat a RAIDZ1, then use the remaining 1TB on the two 4TB hard drives to create a 1TB mirror. Is this configuration possible?

No, it's not possible, or at least very far outside the design. FreeNAS generally assumes each disk is a component of a single pool. You can manually force things from the command line, but you could end up in a bad way someday.

I have set up a TrueNAS installation in Virtualbox to test it but the system isn't allowing me to mix disks of different sizes in a pool. I'm a total noob so I don't understand if I'm missing some steps or this is just not possible.

If what I want to do is impossible, what would you suggest me, provided that I already have a 3TB drive, that I could buy 4TB drives and that the N36L has a total space for 4 drives (or 5, if I use a USB stick for the operating system)?

It won't let you mix disk sizes by default. I believe there's a way to force it to go ahead anyways and use the size of the smallest component device. This would allow you to use the 4TB disks as 3TB disks, and then later if you want to replace the 3TB disk, your pool will recover the additional space.

 

[ciacnorris]

I believe there's a way to force it to go ahead anyways and use the size of the smallest component device. This would allow you to use the 4TB disks as 3TB disks, and then later if you want to replace the 3TB disk, your pool will recover the additional space.

How can I do this?

 

[no_connection]

8GB of RAM and N36L is not really Z1 material to begin with. Or TrueNAS material for that matter. But if you really are inclined to do it then shove 4TB drives in mirror and use the 3TB for backup cause you might very well need it.

 

[JaimieV]

The hardware is absolutely fine for a 3 disk RAIDZ1. I ran a 4TB x 6 RAIDZ2 in an 8 gig Microserver N54L for literally years off the builtin SATA, no trouble.

Ciacnorris, just make a RAIDZ1 with all three disks. You'll lose access to the 1TB excess on the larger drives, but if later you swap in a 4TB for the old 3TB it'll autoexpand and give you the space.

You should also arrange for some sort of backup though. RAID ain't backup, it's availability.

 

[jgreco]

I'll also vote in favor of the N36L, which can also have its memory increased to 16GB. Our little guy sits and soaks up replication traffic all day every day on a (I think) 4 x 4TB RAIDZ2 pool. It's not zippy or awesome, but it's also many years old.

 

[JaimieV]

I had an 8gig N36L as the backup NAS, with a stripeset of four 4T drives. Both the N36L and N54L have been passed on to friends and are still running fine. Ten years old :) Splendid little workhorses.

 

[no_connection]

Good to know, it did say 8GB max and a super slow AMD CPU when I googled but I guess with light load it would be fine enough.

 

[JaimieV]

Yeah, the original spec by HP still says 8GB max, but it's incorrect. Might have been true at the time, if there were only appropriate 4gig sticks back then, but now you can get 8gig sticks that work (and have been able to since at least 2012 when I got mine).

Those microservers are ECC compatible, btw. Both sticks need to be ECC if you have two.

The slow CPUs never affected me - they'd really only get in the way if you were using Plex Server to transcode, but most (all?) client Plex apps nowadays are fine on direct support of modern codecs. Way cheaper to transcode the source files to h.264/265 yourself than buy a new NAS :)

The other limit is if you go 10gigE, I only ever got about 160megabytes/sec from my single-vdev RAIDZ6. Again, not a significant issue at home.

 

[ciacnorris]

Ciacnorris, just make a RAIDZ1 with all three disks. You'll lose access to the 1TB excess on the larger drives, but if later you swap in a 4TB for the old 3TB it'll autoexpand and give you the space.

You should also arrange for some sort of backup though. RAID ain't backup, it's availability.

I have tried to simulate that in Virtualbox but the interface didn't allow me to build a pool with different sized disks.

Anyway I have ordered 3 4TB WD Red Plus, I'll put the 3TB disk in the fourth bay and use it to backup the most important data. Is this what you mean?

Another question: should i put in an SSD as a write or read cache, or it makes little-to-no difference in a N36L?