Expanding a 2 disk mirror

[lupinehorror]

hi all.
got 2 x 2TB drives in a zpool mirror and am thinking about adding a 3rd 2TB drive. what are my options? RAIDZ? and if i were to add a 4th when finances allow it?
thanks in advance for any suggestions.

 

[Dice]

This primer will give you answers to what possibilities you have in terms of expansion patterns.
https://forums.freenas.org/index.ph...ning-vdev-zpool-zil-and-l2arc-for-noobs.7775/

 

[lupinehorror]

This primer will give you answers to what possibilities you have in terms of expansion patterns.
https://forums.freenas.org/index.ph...ning-vdev-zpool-zil-and-l2arc-for-noobs.7775/

hi.
thanks. i've tried to look at that before but the white text on black background actually hurts my eyes!
i'll try and extract the text from it and put it in a plain black on white format.

 

[Stux]

Whatever you do, don't just add the third drive to the pool.

That being said, you *could* use RAIDZ, but getting there from where you are is non-trivial, unless you can backup and restore. Also, RaidZ is not really recommended anymore, but if you understand the risks, you *can* do it. The risk is that the chance of data loss when one of your drives fail is very high, because during the rebuild any minor imperfection in either of the other drives will result in lost data. And drives fail. And they especially fail when under the load imposed during a rebuild.

If you can afford the 4th drive, then adding both new drives as an additional mirror (ie extend the volume with a mirror) is trivial. and as safe as you currently are.

The safest solution would be to upgrade to a 4+ drive RAIDZ2. But again, getting there is non-trivial from where you are (but possible, even without a backup, via some creative partition dancing)

 

[Vito Reiter]

Basically vdevs need to be built with the amount of disks you plan to end with. If you want to keep the data that is currently on the mirror without migrating it all, you'll need to just add a new vdev in another form of redundancy whether it be another mirror, etc. However, you can not just add 1 drive, it will stripe with the rest of the pool and if that one drive fails the whole pool will.

 

[lupinehorror]

thanks all...food for thought.
i think i'll wait until i can add 2 new disks at the same time as an additional mirror.
the data is backed up in three other locations so starting from scratch wouldn't be a problem (apart from the time taken to copy the data back over) so more options are open to me. waiting for the 2 new disks gives me time to properly plan my strategy.
i appreciate your time.

 

[pschatz100]

hi.
thanks. i've tried to look at that before but the white text on black background actually hurts my eyes!
i'll try and extract the text from it and put it in a plain black on white format.

Why don't you just download the Powerpoint version and change the colors?

 

[lupinehorror]

Why don't you just download the Powerpoint version and change the colors?

i did exactly that 5 minutes after my last post...though the main powerpoint link no longer works...had to use the one given near the end of the thread.