Cache Poole Size Reports Correct/ Free+Used Incorrect?

[JeffA]

Hello all -- 

 

Been using unraid for years, never had any problems until now.  With 6.9.X, I created two cache pools, one to aid in speeding up performance the second to hold high io/apps and apps data.  They are as follows:

 

Cache pool 1: 2 x 500 GB SSDs in Raid 1

Cache pool 2: 2 x 2 TB SSDs in Raid 1

 

I wanted to add a third 2 TB drive in Cache pool 2 to bring the capacity up some as I anticipate filling it some day, so I follow the detailed instructions in the unraid doc, I restart the array, it warns me that the 3rd drive will be over written, it does the ZFS equivalent of re-slivering the new drive distributing the data  and parity between all disks as I watch the read/write pattern and it quotes a 3 TB pool capacity (expected size).  

 

Here is the rub.... the reported "used" is correct but the reported "free" is still adding up to 2 TB, the original size of the pool -- any idea why it quotes a 3 TB pool but the "free" bar + "used" bar only adds up to 2 TB? 

Edited January 11, 2022 by JeffA

[JorgeB]

It's a known btrfs issue, it happens when there's an odd number of devices in raid1.

[JeffA]

Gotcha. Thanks.  I guess a little more google effort would have revealed that.