Increasing VDEV size

[NavyLCDR]

Hi!

I've searched for this and would just like to verify the answer that I think I have found. I currently have 2 3TB VDEVs that are striped providing a pool 6TB is size. Each VDEV consists of 2 3TB drives that are mirrored. I would like to replace 1 VDEV with 2 4TB drives that are mirrored so I end up with 7TB total.

What I have read is that I replace 1 3TB drive in a VDEV with a 4TB drive. Let the resilver process complete. Then I can replace the 2nd 3TB drive in the VDEV with a 4TB drive and when it resilvers, the VDEV will automatically increase to 4TB and I will have my 7TB total capacity?

Question 1: is the above true?

Question 2: In order to retain 2 drive redundancy, can I add a 4TB to 1 VDEV making it a 3 disk mirrored set? Once I do that, can I then replace a 3TB drive with a 4TB drive. Once that is resilvered, can I then remove the final 3TB drive?

Thank you for your help!
Very respectfully,
John

 

[sretalla]

What I have read is that I replace 1 3TB drive in a VDEV with a 4TB drive. Let the resilver process complete. Then I can replace the 2nd 3TB drive in the VDEV with a 4TB drive and when it resilvers, the VDEV will automatically increase to 4TB and I will have my 7TB total capacity?

Correct.

Question 1: is the above true?

Yes

Question 2: In order to retain 2 drive redundancy, can I add a 4TB to 1 VDEV making it a 3 disk mirrored set? Once I do that, can I then replace a 3TB drive with a 4TB drive. Once that is resilvered, can I then remove the final 3TB drive?

Yes

 

[NavyLCDR]

Correct.


Yes


Yes

Thank you for your reply! I have one more question, please. Do VDEVs need to be the same size in a striped arrangement? Can I have one VDEV of 2 3TB drives mirrored striped with a second VDEV of 2 4TB drives mirrored for a total of 7TB? Or will only 3TB of the second VDEV be included so I get a total capacity of 6TB?

 

[Etorix]

Do VDEVs need to be the same size in a striped arrangement?

No.

Can I have one VDEV of 2 3TB drives mirrored striped with a second VDEV of 2 4TB drives mirrored for a total of 7TB?

Yes.

Or will only 3TB of the second VDEV be included so I get a total capacity of 6TB?

No. But if you were to make a mirror with a 3 TB and a 4 TB HDD, it would provide a capacity of 3 TB, increasing to 4 TB upon replacing the 3 TB drive by a 4 TB drive or larger. Redundancy and layout are all set at vdev level; at pool level, it always is a stripe of the vdevs, and what vdevs provide is used to the full.

 

[NavyLCDR]

Thank you again for the prompt replies! Sounds like I can do exactly what I want to do!

 

[Arwen]

One last comment. If you have a spare disk slot, you can replace in place. Meaning you install the 4TB disk into the computer, and tell it to replace 1 x 3TB drive with the new 4TB drive.

This allows redundancy to remain at full levels during the re-silver process. And, it can be faster, since it can read the data from either 3TB drive in the vDev.

Once the re-silver is complete, the 3TB drive will no longer be in the vDev, nor part of the pool. In essence, it automates a 3 way mirror replacement. You can then repeat the process for the other 3TB disk in that same vDev.

 

[Geek Baba]

@Arwen quick clarification, could I replace all the disks at the same time or it still needs to be done one by one...

 

[Etorix]

If you have spare slots and replace with the old drives still in place (and full redundancy) you can replace multiple drives at once.

 

[Geek Baba]

Thats great, however is it efficient to do all at the same time or one by one, asking if the copy is sequential and it takes the same time or it runs in parallel, also moving SATA to SAS if thats a factor I need to consider...

 

[Arwen]

At some point replacing too many disks simply slows all of the replacements down. It's a design compromise of your hardware. Only you would be able to determine how many disks you can replace at once, without slowing down the process. We all have different hardware, some home type, others enterprise level.

Note that at one time, it appeared that the TrueNAS GUI only allowed 1 disk replacement at a time. It would queue up the next / others.

Plus, their is a feature of OpenZFS that re-starts a replacement if a second / more disk starts to re-silver. This is to improve performance overall, but slows down the first replacement. This is not a problem if you start all the replacements at the same time.

 

[Geek Baba]

Thanks! I have 2 SATA VDEV each consisting 6 disks in RAIDZ2 that I am going to replace with larger SAS drives, so I am planning to replace one disk first to capture the baseline, then add 5 at the same time to see how it goes, then do the next one with 6 of them simultaneously. The hardware is enterprise with 256gig of ram and 12 Xeon cores. Having said that I didn't understand this statement, will I be able to replace the drives simultaneously from GUI with TrurNAS 13?

Note that at one time, it appeared that the TrueNAS GUI only allowed 1 disk replacement at a time. It would queue up the next / others.

 

[Arwen]

Sorry, I just don't know.