Two identical SSD drives, cache pool showing wrong size after one was disconnected

[Senson]

Hello,

I have a cache pool that consists of two 500GB SSD's. Originally, the filesize showed as 500GB which is what I expected for a RAID1.

 

I had an accident where one of the drives got disconnected and when I reconnected it, it appeared as though it stopped being RAID1. The filesize started showing 750GB. I tried rebalancing, stopping the array, rebooting, etc. but it still shows 750GB.

 

Attached are photos of the config, and the cache status. I also noticed that in the balance status, it shows the following. Does this look correct for RAID1?

 

 

Data, RAID1: total=118.00GiB, used=95.00GiB

System, single: total=32.00MiB, used=48.00KiB

Metadata, RAID1: total=1.00GiB, used=496.30MiB

GlobalReserve, single: total=52.44MiB, used=0.00B

[JorgeB]

System is using single profile, run a balance to raid1

[Senson]

The balance didn't sort things out properly. I ended up following jonp's instructions here: 

 

 

 

STARTING POSITION:  Two disks or more in a btrfs cache pool; array is running.

 

1 - Stop Array

2 - Unassign the disk from cache 2 (but do not change the # of slots)

3 - Physically detach cache 2 from the system (remove power / SATA)

 4 - Start the array

 5 - Open the log, notice a "balance" occurring (you'll see a number of entries such as this:

   Quote

Jun 2 08:49:55 Tower kernel: BTRFS info (device sdf1): relocating block group 36561747968 flags 17

6 - When the balance completes, the device you physically removed will be deleted from the cache pool.

Looks better now:

Data, RAID1: total=119.00GiB, used=105.29GiB

System, RAID1: total=32.00MiB, used=48.00KiB

Metadata, RAID1: total=1.00GiB, used=516.38MiB

GlobalReserve, single: total=99.72MiB, used=0.00B

 

 

TL;DR I removed the second cache disk, let things settle, then re-added it back in.

[JorgeB]

What you did was a more complicated way of running a balance, likely you didn't use the correct command, but as long as it worked...

[denishay]

Had a similar problem with 2 TB Samsung 870 EVO. They were happily in RAID1, then suddenly without explanation went into "single" mode and cache was showing the wrong size.

 

No amount of balance worked (the option did reset without letting me run a balance and the command line equivalent didn't work).

 

I had to change my shares/docker/vm to not use cache, removed both drives, formatted both, then created cache again with one drive, copied data back and then added the second one. There I had the RAID1 balance working. Everything is back in order.