Re: ENOSPC errors during raid1 rebalance

[Eugene Crosser <crosser@average.org>]

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Hello,

I want to report that I have the same problem as Michael Russo, except in my
case there is definitely *a lot* of free space.

I had ext4 on a 1Tb LVM mirror. The filesystem was 96% full, with many multi-Gb
files. I successfully converted it into btrfs, removed ext2_saved subvolume, but
did *not* defragment or balance.

Then I added two fresh 4Tb disks to the filesystem, and tried to convert it to
raid1. My plan was to then delete the original LVM disk and have all my data
migrated to the new 4Tb disks under btrfs mirror.

But balancing cannot complete with the same symptoms:

[...]
[12746.391828] block group has cluster?: no
[12746.391830] 0 blocks of free space at or bigger than bytes is
[12747.420098] btrfs: 35 enospc errors during balance

root@pccross:~# btrfs fi sh
Label: 'export'  uuid: 02f39e9d-9115-4a79-9015-a3a9decb87cf
	Total devices 3 FS bytes used 798.15GB
	devid    3 size 3.64TB used 855.03GB path /dev/sdd1
	devid    2 size 3.64TB used 855.00GB path /dev/sdc1
	devid    1 size 891.51GB used 175.48GB path /dev/md5

Btrfs v0.20-rc1

root@pccross:~# btrfs fi df /export
Data, RAID1: total=849.00GB, used=650.25GB
Data: total=175.48GB, used=145.64GB
System: total=32.00MB, used=136.00KB
Metadata, RAID1: total=6.00GB, used=2.21GB

root@pccross:~# uname -a
Linux pccross 3.13.0-17-generic #37-Ubuntu SMP Mon Mar 10 21:44:01 UTC 2014
x86_64 x86_64 x86_64 GNU/Linux

Attempt "btrfs device delete" fails with the same "no space" diagnostic.

I am running defragmentation on all files bigger than 1Gb now, and see what
happens. If that does not help, is there any other advice? I can collect
debugging data if needed.

Thanks,

Eugene


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