Re: btrfs freezing on writes

[kjansen387 <kjansen387@gmail.com>]

I have tried to rebalance metadata..

Starting point:
# btrfs fi usage /storage
Overall:
     Device size:                  10.92TiB
     Device allocated:              7.45TiB
     Device unallocated:            3.47TiB
     Device missing:                  0.00B
     Used:                          7.35TiB
     Free (estimated):              1.78TiB      (min: 1.78TiB)
     Data ratio:                       2.00
     Metadata ratio:                   2.00
     Global reserve:              512.00MiB      (used: 0.00B)

Data,RAID1: Size:3.72TiB, Used:3.67TiB (98.74%)
    /dev/sdc        2.81TiB
    /dev/sdb        2.81TiB
    /dev/sda     1017.00GiB
    /dev/sdd      840.00GiB

Metadata,RAID1: Size:6.00GiB, Used:5.09GiB (84.86%)
    /dev/sdc        3.00GiB
    /dev/sdb        3.00GiB
    /dev/sda        1.00GiB
    /dev/sdd        5.00GiB

System,RAID1: Size:32.00MiB, Used:608.00KiB (1.86%)
    /dev/sdb       32.00MiB
    /dev/sdd       32.00MiB

Unallocated:
    /dev/sdc      845.02GiB
    /dev/sdb      845.99GiB
    /dev/sda      845.02GiB
    /dev/sdd     1017.99GiB

I did:
# btrfs fi resize 4:-2g /storage/
# btrfs balance start -mdevid=4 /storage
# btrfs fi resize 4:max /storage/

but the distribution of metadata ended up like before.

I also tried (to match the free space of the other disks):
# btrfs fi resize 4:-172g /storage/
# btrfs balance start -mdevid=4 /storage
# btrfs fi resize 4:max /storage/

again, the distribution of metadata ended up like before..

Any other tips to rebalance metadata ?


On 10-Apr-20 01:07, Zygo Blaxell wrote:
> On Thu, Apr 09, 2020 at 11:53:00PM +0200, kjansen387 wrote:
>> btrfs fi resize 1:-1g /export;           # Assuming 4GB metadata
>> btrfs fi resize 2:-2g /export;           # Assuming 5GB metadata
> 
> Based on current data, yes; however, it's possible that the device remove
> you are already running might balance the metadata as a side-effect.
> Redo the math with the values you get after the device remove is done.
> You may not need to balance anything.
> 
>> btrfs balance start -mdevid=1 /export;   # Why only devid 1, and not 2 ?
> 
> We want balance to relocate metadata block groups that are on both
> devids 1 and 2, i.e. the BG has a chunk on both drives at the same time.
> Balance filters only allow one devid to be specified, but in this case
> 'devid=1' or 'devid=2' is close enough.  All we want to do here is filter
> out block groups where one mirror chunk is already on devid 3, 4, or 5,
> since that would just place the metadata somewhere else on the same disks.
> 
>> btrfs fi resize 1:max /export;
>> btrfs fi resize 2:max /export;
>>
>> Thanks!
>>
>>