ZFS Keep a specific filesystem on a designated disk

K

kurld

Hello,

Let's say that I have a zpool with 2 disks - disk01 and disk02. On the zpool there are zfs file systems- FS01, FS02, FS03.
I'd like to organize the fs allocation in a way that FS01 resides exclusively on disk01, FS02 on disk02 and FS03 is mirrored between disk01 and disk02.
For those of you familiar with AIX, is there a concept of LPs and PPs on zfs? Can file systems be moved between disks?
 
Not possible with ZFS. Not on a vdev that contains both disks. If you want something like that you're going to have to create three separate pools.
 
kurld said:
... and FS03 is mirrored between disk01 and disk02.
Click to expand...

Part of the point of ZFS is you don't have to micro manage this. If you had a striped pool and you wanted to add some redundancy for the FS03 filesystem in your example, you can get limited degree of control with the zfs set copies=2 <filesystem> to ensure data gets written to 2 independent vdevs. However rather then adding redundancy like this you would be far better off using a mirror or RAID-Z pool and let ZFS handle things behind the scenes.
 
what you can do is make 2 separate pools.
Code: 
zpool create singlepool1 disk1
zpool create singlepool2 disk2

then make 2 vzvols one on each disk.
Code: 
zfs create -V 100G singlepool1/zvol1
zfs create -V 100G singlepool2/zvol2

then make a mirrored pool out of zvol1 and zvol2
Code: 
zpool create mirrorpool1 mirror /dev/zvol/singelpool1/zvol1 /dev/zvol/singelpool2/zvol2

now you have 3 pools first pool on disk 1 second on disk 2 and the third on disk 1 and 2, the nice thing about zvols is that you can easily expand them to make mirrorpool1 bigger i have not tested the comands so dont copy past them. :)
 
Last edited by a moderator:
junovitch@ said:
(...)If you had a striped pool and you wanted to add some redundancy for the FS03 filesystem in your example, you can get limited degree of control with the zfs set copies=2 <filesystem> to ensure data gets written to 2 independent vdevs.(...)
Click to expand...
As far as I know, copies=N>1 does not guarantee that the copies will be written to independent/different vdevs.

cellini: I think there's still a chance of deadlock when running a zpool on top of a zvol in the same kernel. Should be "fine" to use geom mirror + ufs though. :)
 
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