Expanding a volume with a new vdev

[MarkS-Indy]

I have an existing 10 disk volume (4TB disks in RaidZ2) in a 20 bay server. I am preparing to add 10 8TB disks in a RaidZ2 as a new vdev. By expanding the volume with this new vdev, will it utilize the 8TB disks as 8TB disks, or use them as 4TB disks? Thanks.

 

[nojohnny101]

Yes. Drive size is determined by the smallest drive size per vdev.

You're good to go!

 

[MarkS-Indy]

OK, so let me get this right. I create a new RaidZ2 vdev with my array of 10 8TB drives, then expand my existing volume with the new vdev and there is no risk of losing all the existing data in the current vdev, correct? And, my volume should now show an expanded capacity of approximately 88TB. Am I missing anything? I just want to be sure that once I commit this new array to the volume, that I will be getting the capacity I am paying for, and that I will not be losing existing data in the bargain. Thanks for any help that can be given this newbie.

 

[nojohnny101]

Ok I can respect you being cautious, too many people on here have added drives in the wrong way to their pools and then get stuck up a creek without a paddle.

Good news there is no way you will lose your data, no matter how you add those drives to your FN box. The only caution you have to look out for is to add the 8 new drives to your existing pool with the correct party (raidz1, raidz2, radiz3, etc.). Many people make mistakes when they try and add 1 or 2 drives or some low number of drives, and then accidentally stripe it as a single disk with no parity. The danger is that once you add a vdev to a pool, there is no way to remove it, without destroying the whole pool (the new vdev and all other previous vdevs) and rebuilding.

If you plug all 8 drives in and add them at the same time (which you need to do, you obviously can't add drives one by one) then you will avoid the "added a single drive to my existing pool, oh crap". Just make sure it says "raidz2" when you are adding them and you're good to go. If you happen to mess up and add the 8 new drives as a new poo instead of a new vdev, no biggie (this would happen if you don't select your existing pool when you add the new drives. if you don't do that, it assumes you want to add a new pool). You can destroy the new accidental 8 drive pool and then add it again properly as a vdev. no biggie.

I hope I made this more clear, not muddier. Ask more questions if you have them. Best practice is to follow the manual procedure for this: http://doc.freenas.org/9.10/storage.html#volumes

 

[gpsguy]

Instead of using the word expand, what you want to do is EXTEND your existing volume.

I don't know if you are using 9.x or Corral, but for 9.x you can read about extending your volume in section 8.1.1 of the docs.

 

[MarkS-Indy]

Instead of using the word expand, what you want to do is EXTEND your existing volume.

I don't know if you are using 9.x or Corral, but for 9.x you can read about extending your volume in section 8.1.1 of the docs.

Sorry about the incorrect terminology. I am using FN 9.3. I have spent the last few hours reading the documentation and I believe I feel comfortable at this point to proceed in extending my volume once I have added another 16GB of RAM.

 

[gpsguy]

Sorry about the incorrect terminology. I am using FN 9.3.

No problem. It's just easier to find help if you use the correct terminology.

BTW, if you'd like a PDF or ePub version of the docs for FreeNAS 9.3, you can download one via a link in my signature.

 

[nojohnny101]

Sounds like your taking your time to do it properly, that is how you do not make mistakes.

Kindly report back to let us know success or otherwise to benefit others in the future who search.

 

[MarkS-Indy]

Sounds like your taking your time to do it properly, that is how you do not make mistakes.

Kindly report back to let us know success or otherwise to benefit others in the future who search.

Will do. Currently waiting for "burn-in" on 4 drives, and delivery of 16GB of ECC RAM to add to the server. Hoping to be able to do the install and have everything up and running this weekend. Thanks again to you and gpsguy.

 

[I-Tech]

so .. question about this concept..
adding 10x 8TB drives but only utilizing 4TB out of them (for now) is what you are planning.
is the option to replace each of the existing 10x 4TB drives one at a time with the new 8TB drives and thereby gaining the space something to think about?
then there would be 10x 8TB drives with the increased available disk space and you still have 10 empty slots. (with 10x 4TB drives left over)
just a question... as I may also be looking at changing / adding drives.

 

[Robert Trevellyan]

adding 10x 8TB drives but only utilizing 4TB out of them (for now) is what you are planning.

No, the OP will get full use of the capacity of the new drives, because they will be in a separate vdev. ZFS only uses the smallest capacity for drives of mixed size within the same vdev.

 

[MarkS-Indy]

so .. question about this concept..
adding 10x 8TB drives but only utilizing 4TB out of them (for now) is what you are planning.
is the option to replace each of the existing 10x 4TB drives one at a time with the new 8TB drives and thereby gaining the space something to think about?
then there would be 10x 8TB drives with the increased available disk space and you still have 10 empty slots. (with 10x 4TB drives left over)
just a question... as I may also be looking at changing / adding drives.

I considered that at one point, but adding each drive is tedious in that as you add a drive, as I understand it, the entire volume has to be re-silvered. Not only does that take a very long time (having had one drive fail in the past and going through that process), it places a lot of stress on the drives, considering that you would do that 10x. My plan is to fill my 10 empty bays with 8TB drives, create a new vdev with them, then add them to the pool by extending/expanding the volume. The current 10 drive vdev will still be intact and utilized.
Does that explain what is going on here?

 

[I-Tech]

My profound apologies to everyone .. I have (had) been sifting through these forums reading many (many) posts where people had asked about disk sizes and vdev expansions.. and when I looked at this one.. I didn't click that it was on a separate vdev.
(just re-read the OP "..as a new vdev.." and said to myself 'duh')
(I'll be quietly sitting in the corner for the rest of the morning)

No, the OP will get full use of the capacity of the new drives, because they will be in a separate vdev. ZFS only uses the smallest capacity for drives of mixed size within the same vdev.

I considered that at one point, but adding each drive is tedious in that as you add a drive, as I understand it, the entire volume has to be re-silvered. Not only does that take a very long time (having had one drive fail in the past and going through that process), it places a lot of stress on the drives, considering that you would do that 10x. My plan is to fill my 10 empty bays with 8TB drives, create a new vdev with them, then add them to the pool by extending/expanding the volume. The current 10 drive vdev will still be intact and utilized.
Does that explain what is going on here?

 

[MarkS-Indy]

Update on this: I had a bit of a problem with the SAS controller once all 20 drives were snuggly in their bays. Took a bit of research, but was able to solve the issue, the issue being that the server was not able to get to the OS boot menu. I had to reflash the SAS controller and get rid of its BIOS. After that, FreeNAS booted right up.
Extending the volume went perfectly smoothly after that, and I now have all 20 drives contributing their space to the volume (without the loss of one bit of data :)).
Once again, thanks for the help.