Change Raid 6 to 10 bug search

Hi all, doing a little due diligence here hoping to tap your collective brains before embarking on the change. I have a 5x4TB RAID 6 install right now and it’s been doing fine, but about to start committing family photos to it and have decided based on the state of RAID 6, I probably need to move to RAID 10 to prevent a non-recoverable failure down the road. (yes I will have a back up plan as well, hopefully a 2nd Rockstor) Planning on removing one drive from existing pool, and re-balancing. Then copy all data to that drive for safety ( I still have all the original data scattered around, but if I can keep what I’ve got it will save time), then convert 4 remaining disks in RAID 6 pool to RAID 10.
Anybody try anything similar?
Run into any problems?
Any sage advice beyond back up my data before I start?

@suman_chakravartula @phillxnet Any opinions on using the Rockstor UI vs. CLI?
I plan on using the Rockstor UI unless someone has a good reason not to.

For the curious, I’ve been running RAID 6 for light duty home use for a year with no problems other than one I caused the first week by hot swapping the first disk in the pool, and not being able to recover the pool.

Thanks in advance for any insight.

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Hi @D_Jones. The balance could get tricky if you don’t have much free space in your RAID 6 Pool. But if all your data could fit into one 4TB drive as you seem to suggest you should be fine. I have converted RAID 6 into RAID 10 before and it does work as expected. I would make sure that the balance operation at every step finishes, and that the pool is fully balanced before moving to the next step. You can use btrfs fi show /mnt2/<pool_name>, btrfs fi df /mnt2/<pool_name> and btrfs fi usage /mnt2/<pool_name> to verify thoroughly before moving on.

I would use the UI and then jump to the CLI if the balance job fails on the UI. If balance fails, you’ll need to use filters and balance up to a few times. See this. In your case, since your usage is < 4TB, its very likely that you’ll experience will be smooth.

@suman Thanks for the reply, my data is very light, only about 400GB.
When I remove the 5th drive, I’m expecting BTRFS to automatically kick off a balance and distribute the data at RAID 6 across the remaining 4 drives (I know an odd number is preferred for RAID6, do you see any problems with this). After that balance finishes, I’ll set up the removed drive as it’s own pool and copy my data there. Once data is copied, I’ll convert the RAID6 to RAID10, which should also automatically kick off a balance if I’ve done my homework. Thanks for the feedback on the process and your experience. Also, thanks for all the development work, the UI and file access both feel much faster and cleaner. Your effort is definitely paying off. Wish I could be more help.

Your expectations and assumptions are correct. Not sure about about your raid 6 and of number question, others may be able to provide an answer.

Thanks for your gratitude, great to have you engaged in our community!

As a user who has been converting a lot I’ll say a few words.

My pool has over the time been converted many times. I have gone from RAID6 -> RAID5 -> RAID6 -> RAID10 -> RAID1, where I am at now.

My pool had much larger amount of data on it than yours.

I didnt experience any problems with any of the conversions, they just worked as expected.
Only thing to be alert to, is that if any data is written to the pool during conversion, it will be written in the old RAID pattern, and wont get converted. So you can end up with both RAID6 and RAID10 data in your pool (BTRFS supports this). You’ll have to check that all data are converted when the job is finished.

But otherwise I dont see why your conversion should not work, unless you are unlucky to have a failure of some sort during conversion.


Couple of gotchas:

  • if you created pool long time age (very long time ago) leaf size might be still 4k, nowadays when you create a pool (FS) it will default to 16K, which gives a LARGE performance boost
  • as long as your pool (FS) is in an absolute tik tok state you can convert freely ! Just be advised that raid 5 / 6 had tendency to silently introduce problem even with file system related data. I’ve seen so many people crashing and burning I would NOT attempt conversion without a full backup.
  • IF you have full backup AND there are no indications of a problem with your pool (FS) just convert whole thing in place !!! btrfs raid 10 does not need even number of disks !

@Tomasz_Kusmierz Thanks for the feedback, and the tip on the number of disks, thought I was destined to have a spare disk installed for a while. I turned each share into a tar.gz now I just need to find a place to park them before I commence. For clarification is 12 months far enough back to worry about 4k leafs? Is there a command to check that?

Just encrypt those files with something like aes 2048 or better and spit it out into any random proxy server … NSA and CIA will provide with very redundant backup of your archive … you know just in case :stuck_out_tongue:

@suman Happy to report conversion done, all 5 disks to RAID10 without a problem. One thought for a potential UI improvement. As I ran the balance and also a scrub, if I wanted to see the progress I needed to reload the page and then pick the appropriate tab. Adding an update button above the status tables might be a nice addition. I’m sure you have more pressing issues, but when you get around to fine tuning this might be worth the time. Thanks again to all that provided advice.