ZFS pool for backup with different old disks. Best approach?

[helloha]

Dear All,

I build a server with a nice gigabit connection to my workstation.

I got a bunch of older disks laying around. The idea is to build a time machine backup server.

I got: 2x160gb 1x320gb 1x750gb 1x1000gb 1x2000gb

Is it possible to get any kind of pairity by combining these disks in a pool? It is not that important since it is a backup server but it would be nice. having the possibility to add a file server over time would be nice.

And if would want to grow the size of the capacity, is it possible to just replace any disk?

Regards,
Karel

 

[sub mesa]

What you can do is combine the 320GB + 750GB into one '1000GB' drive. Then use a mirror with the other 1000GB drive, or a RAID-Z with the 1000GB and 2000GB drive. However, the 2000GB drive will have half of its capacity underutilised this way.

So the simplest would be to put all those disks in a ZFS stripe and live without redundancy. If this is your backup server that should be okay depending on circumstances. The downside is that ZFS can no longer fully protect your data against bad sectors - let alone drive failure.

In my own opinion, I would stop using drives under 1TB because these old drives often consume much more power than modern drives. For example, those two 160GB drives can consume more power than four modern 2TB drives. If the system is online 24/7, this might be important.

Of course, ZFS works best with new hardware built specifically for ZFS. This way you can save on hardware costs by not buying stuff you do not need (TLER disks, hardware RAID controller. BBU battery protection, high-powered CPU) and using that saved power to invest in more disks and more RAM memory which ZFS likes.

 

[helloha]

Thanks for the tip!

Do you know if it is possible to change drives when I would put everything in stripe.

Lets say over time I want to swap a 160gb with a bigger drive. Do I lose everything or is there a way to tell the system to duplicate part of the data first on the new drive, so I can remove the old one.

Cheers!
Karel.

 

[sub mesa]

You can remove the 320GB+750GB harddrives in the future and replace it with a single 1TB drive, yes.

What you can't do with ZFS, is remove drives permanently. If you have a 4-disk stripe in ZFS, you cannot turn this into a 3-disk stripe by removing a single disk. You can only replace or add disks. Thus, the pool can only stay the same or grow in size; it cannot shrink.