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Comment by kogir | Hacker News Reader

What exactly did you try? On the surface that sounds pretty straightforward.

The problem I most often see people run into is trying to use mismatched drives they have lying around. With ZFS you’ll have a much better time just purchasing matched disks to fit the zpools you have in mind. It was built for well planned, huge arrays in datacenters and that legacy shows.

I’ve used ZFS for years in a variety of configurations on Solaris, FreeBSD and macOS. My only training was the Solaris and FreeBSD man pages, so it’s not that dark an art.

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I have a 4-bay QNAP x64 appliance that I wanted to put a full Linux distro. I wanted to have a matched 3-drive raidz pool for /var, /usr/local and /home and have the rest of the system live off an SSD.

My goal was to have a media server for the home with DVR capabilities to use a Hauppage USB tuner to use within Plex. QNAP pulled DVB support 2-3 years ago, unfortunately so a native solution wasn't working. I considered FreeNAS but LCDproc is not available which is a must have for me.

I tried several ways of going about this: installing the system to the SSD and copying over those specific directories to the raidz pool with appropriate changes to mounts. I tried doing the debootstrap method, and chrooted to create the raidz within the new install.

However, either I ran into issues in either configuring grub, or the remapped directories not mounting at boot. I am sure there was a simple element that I was missing, but within the time constraints of personal life and a skillset not to par with an IT admin, I gave up and relegated my self to the QNAP environment, without the DVR function I so badly wanted.

So, what does one do if all they have laying around are mismatched drives?

You can partition your drives based on the size of the smallest and make your pool on those partitions.

You _can_ mix drives, but you'll get the worst from each. For each vdev (mirror pair, or raid stripe) writes will be limited by the slowest drive, and space will be limited by the smallest drive.

So if they're not highly mismatched, it can work ok. For example if you have a 1 TB and a 1.5 TB disk, but from the same series and as such with otherwise similar spec, it would work fine as a mirror vdev. Write speed will be limited to the slowest of them (most likely the 1 TB), and you'd only get 1 TB of available space, but it's more than nothing.

Ah, ok. I have 2 3TB and a 4TB running on a Proxmox v3 system. Was wanting to upgrade to Proxmox v5 and try ZFS.

The 4TB is a different make than the 2 3TB drives, though.

I've been running a mixed-make mirror array for half a year now. Like I said, speed is limited by slowest drive but apart from that it works just fine.

Thank you. I appreciate the info.

Note it's probably not a good idea (if possible) to mix 512 and 4096 byte sector drives in the same vdev.

If you create the pool with ashift=12, you're fine.

The only hazard is if you have an ashift=9 pool (the default, IIRC) and later add a 4096 byte sector drive, you might lose some write perf. It probably doesn't matter for homelab use.

There aren't many 512 byte drives any more. You'll be fine.

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