On 7/18/2016 at 4:46 AM, JorgeB said:

How do I remove a cache pool disk?

 

A few notes:

-unRAID v6.4.1 or above required, upgrade first if still on an older release.

-Always a good idea to backup anything important on the current cache in case something unexpected happens

-You can only remove devices from redundant pools (raid1, raid5/6, raid10, etc) but make sure to only remove one device at a time, i.e., you can't remove 2 devices at the same time from any kind of pool, you can remove them one at a time after waiting for each balance to finish (as long as there's enough free space on the remaining devices).

-You can't remove devices past the minimum number required for the profile in use, e.g., 3 devices for raid1c3/raid5, 4 devices for raid6/raid10, etc, exception is removing a device from a two device raid1 pool, in this case Unraid converts the pool to single profile.

-Some Unraid releases like current stable v6.8.3 permit removing devices from non redundant pools, but this is not officially supported, the pool itself can't be encrypted and the device being removed must remain connected while the pool is balanced to the new profile, there might be other gotchas so proceed with care.

 

 

Procedure:

 

• stop the array
• unassign pool disk to remove
• it's OK to reorder remaining pool members if you want (but see point below), i.e., you had a three device pool and removed cache2, you can assign cache3 to slot2 before starting the array (you can also do it later)
• while it's OK to reorder members it's currently not OK to change the number of cache slots at the same time you remove a device, you can do that after the pool is balance down, i.e., just don't do both things at the same time.
• start the array (after checking the "I'm sure" box next to the start array button)
• a balance and/or a device delete will begin depending on the profile used and number of pool members remaining, wait for cache activity to stop, the stop array button will be inhibited during the operation, this can take some time depending on how much data is on the pool and how fast your devices are.
• when the cache activity stops or the stop array button is available the replacement is done.

 

 

 

Quote

-Some Unraid releases like current stable v6.8.3 permit removing devices from non redundant pools, but this is not officially supported, the pool itself can't be encrypted and the device being removed must remain connected while the pool is balanced to the new profile, there might be other gotchas so proceed with care.

 

So I'm on Version: 6.10.3 and have two 1TB SSDs as part of the cache pool. I'd like to split the pool up into two, which means i need to remove one of the drives, but they are encrypted. Per the above, I can't use this method.

 

How do I remove one of the two cache disks in a pool where the drives are encrypted?

You may get better advice from someone else, but if it were me, I'd back up everything currently on the pool, remove both devices from the current pool, blkdiscard both /dev/* members, being VERY careful to select the correct disks, then recreate 2 pools how you want them.

 

Given how fiddly BTRFS can be, add encryption issues on top, and I'd be making backups of backups when using an encrypted BTRFS setup even on a normal basis, nevermind when trying to reconfigure things. If something goes wrong, file system recovery becomes almost impossible when encryption is involved.

18 hours ago, Salzgablah said:

So I'm on Version: 6.10.3 and have two 1TB SSDs as part of the cache pool.

Is this a redundant or non redundant pool? Above highlighted text is for non redundant pools only.

Redundant pool.  I went the path of moving all cache files off the pool onto the array, then started fresh with only one drive in the cache pool. Took a bit longer to move everything off then back on (appdata and vm's), but didn't want to risk it.

46 minutes ago, Salzgablah said:

but didn't want to risk it.

That's fine, but like mentioned that text only applies to non redundant pools.