Confusion on zpool and Vdev in freenas

[fresto]

Hi guys,

Heads up, i've never used a nas before.

I finished up reading cyberjock pp on freenas guide but i'm confused with the relation between zpool and vdev (ZFS) in the freenas gui.

I've installed freenas on vbox for testing, create a volume with raid-z2 with 4*"2TB" drives.

Question is which is zpool and which is vdev? Does the 7.9TB refer to zpool and 3.7TB refer to vdev?

 

[Xyrgh]

I'm fairly noob myself and was confused, as there are interchanging terms like 'volume and zpool. Basically vdev is a baremetal collection of disks, be it a stripe, mirror, RaidZ1,Z2,Z3, a zpool is a collection of vdevs. You can add vdev to a zpool, but you can't add a drive to a vdev.

As much as I know, your 'master' is a zpool consisting of a RaidZ2 vdev. If you click on your volume 'master' it will show your RaidZ2. If you go ahead and chuck two more disks in the system, then extend the volume (say with a mirror) then look at volume status, it will show your zpool.

ie.:

I''ve done this on my test machine by creating a mirrored vdev, then adding a spare stripe. If you had a RaidZ2 vdev and a mirror vdev, this would show (where 'spares is, I assume) as mirror.

I hope that makes it a little clearer, as I'm also trying to get my head around all of this.

 

[Bidule0hm]

Two things I hope should make everything clear: https://forums.freenas.org/index.php?threads/comprehensive-diagram-of-the-zfs-structure.38865/ and https://forums.freenas.org/index.php?threads/the-faq.30209/#post-194030 ;)

 

[Xyrgh]

That diagram should be a sticky! Explains it much better than words.

It does get a bit confusing, because I believe a lot home users would just set up one zpool with a RaidZ2 vdev or similar and call it a day, so when you start getting into expanding the zpool, it doesn't make sense initially, as the GUI doesn't really reference zpool, at least not that I can see.

 

[Bidule0hm]

A pool is a volume in the GUI... yeah I know... :)