Hello everyone!

First, thanks for amazing work on btrfs filesystem!

Now the problem:
I use a ssd as my system drive (/dev/sda2) and use daily snapshots on
it. Then, from time to time, i sync those on HDD (/dev/sdb4) by using
btrfs send / receive like this:

ionice -c3 btrfs send -p /ssd/previously_synced_snapshot /ssd/snapshot-X
| pv | btrfs receive /hdd/snapshots

I use pv to measure speed and i get ridiculos speeds like 5-200kiB/s! 
(rarely it goes over 1miB). However if i replace the btrfs receive with
cat >/dev/null - the speed is 400-500MiB/s (almost full SSD speed) so I
understand that the problem is the fs on the HDD... Do you have any idea
of how to trace this problem down?

Note: I had quota enabled on that hdd before and disable id since it was
making problems.

Any help is appreciated. Thanks!

here is some more information:
$ uname -a
Linux nick-G55VW 3.16.0-28-generic #37-Ubuntu SMP Mon Dec 8 17:15:28 UTC
2014 x86_64 x86_64 x86_64 GNU/Linux

$ btrfs --version
Btrfs v3.14.1

$ sudo btrfs fi show
Label: none  uuid: 5f0ca1d2-b2c4-499e-a7df-efb2590b6502
    Total devices 1 FS bytes used 169.68GiB
    devid    1 size 300.00GiB used 300.00GiB path /dev/sda2

Label: 'hdd'  uuid: 35423c57-13e0-44e9-bacb-6f467ec4b885
    Total devices 1 FS bytes used 310.47GiB
    devid    1 size 447.44GiB used 447.44GiB path /dev/sdb4

Btrfs v3.14.1


btrfs fi df / # i create a readonly snapshot of this on every boot to
/mnt/snapshots (on the same SSD)
Data, single: total=289.99GiB, used=163.22GiB
System, single: total=4.00MiB, used=48.00KiB
Metadata, single: total=10.01GiB, used=6.46GiB
unknown, single: total=512.00MiB, used=0.00

btrfs fi df /home/ # i create a readonly snapshot on every GUI login
Data, single: total=289.99GiB, used=163.22GiB
System, single: total=4.00MiB, used=48.00KiB
Metadata, single: total=10.01GiB, used=6.46GiB
unknown, single: total=512.00MiB, used=0.00

btrfs fi df /mnt/snapshots # when syncing to HDD this is the source
Data, single: total=289.99GiB, used=163.22GiB
System, single: total=4.00MiB, used=48.00KiB
Metadata, single: total=10.01GiB, used=6.46GiB
unknown, single: total=512.00MiB, used=0.00

btrfs fi df /mnt/snapshots_hdd/@snapshots/ # the destination on the HDD
for syncing with btrfs receive
Data, single: total=436.41GiB, used=302.74GiB
System, single: total=32.00MiB, used=48.00KiB
Metadata, single: total=11.00GiB, used=7.47GiB
unknown, single: total=512.00MiB, used=12.00KiB