I have a btrfs RAID1 array (two 891GiB partitions on two HDDs) on my laptop. When I run btrfs balance it takes a huge amount of time to complete.
I know if I would like to balance the whole filesystem it would take forever, that's why I'm using the -usage filter like this; I've put this in the for loop because I don't always know with which number to start.
for i in {1..100}; do sudo btrfs balance start -dusage=$i /my/mount/path/; done
In this loop, sudo only asks my password the first time, or if the balance took a lot of time. This prints about 20 times
Done, had to relocate 0 out of 868 chunks
And then after taking a huge amount of time it prints
Done, had to relocate 1 out of 868 chunks
So it means it has only moved 1GB (or 200MB) of data. It just shouldn't take that much time to move just 1GB of data, I can copy much more data to this filesystem in a tenth of the time.
This is the entry on my fstab:
UUID=<the uuid> /my/mount/path/ btrfs defaults,noatime,compress=lzo 0 0
I also have to mention that I usually make and also delete snapshots just in case I make something wrong.
sudo btrfs subvolume list /my/mount/path/
ID 5238 gen 178224 top level 5 path SNAP/snap-2017-04-15
ID 5270 gen 178229 top level 5 path SNAP/snap-2017-04-17
ID 5272 gen 178228 top level 5 path SNAP/snap-2017-04-21
ID 5276 gen 178230 top level 5 path SNAP/snap-2017-04-25
ID 5284 gen 178232 top level 5 path SNAP/snap-2017-05-04
ID 5290 gen 178231 top level 5 path SNAP/snap-2017-05-10
ID 5291 gen 178229 top level 5 path SNAP/snap-2017-05-11
ID 5309 gen 178225 top level 5 path SNAP/snap-2017-05-11-22-52-30
ID 5310 gen 178226 top level 5 path SNAP/snap-2017-05-13
ID 5311 gen 178232 top level 5 path SNAP/snap-2017-05-15
ID 5312 gen 178227 top level 5 path SNAP/snap-2017-05-17
ID 5313 gen 178227 top level 5 path SNAP/snap-2017-05-18
I also have quotas enabled to help me see how much has been modified between snapshots.
sudo btrfs qgroup show /my/mount/path/
qgroupid rfer excl
-------- ---- ----
0/5 774.25GiB 910.87MiB
0/3098 142.21GiB 0.00B
0/3119 39.38GiB 16.00EiB
0/5226 0.00B 16.00EiB
0/5228 0.00B 16.00EiB
0/5233 48.00KiB 16.00EiB
0/5236 96.00KiB 16.00EiB
0/5238 785.18GiB 46.57GiB
0/5270 768.99GiB 1.22MiB
0/5272 768.73GiB 1.36MiB
0/5276 766.70GiB 12.70MiB
0/5284 768.55GiB 3.33MiB
0/5290 772.23GiB 964.00KiB
0/5291 772.23GiB 912.00KiB
0/5309 773.77GiB 608.00KiB
0/5310 773.78GiB 1.09MiB
0/5311 773.56GiB 1.66MiB
0/5312 773.55GiB 2.16MiB
0/5313 774.32GiB 147.49MiB
The 16.00EiB must be some kind of mistake, Who has such a HDD?
Why does balance take that long to complete? I really like the btrfs features, so I prefer to stay with it.
