The recent announcement from Suse Enterprise Linux that Btrfs was production-ready raised some suspicions. The last time I tested btrfs (not very long ago) the primary issues were excessive CPU utilization and filesystem space that seemed to disappear into nowhere. So, as a quick test, I put together an OpenSuse 12.2 (3.4.6-2.10-desktop, OpenSuse 12.2) 64-bit VM (ESX) with 4 vCPUs, 4GB RAM, the OS disk and a 6GB striped LVM filesystem consisting of 4 4-GB virtual disks.

The results were consistent with my previous test of btrfs on physical hardware: high CPU utilization and excessive filesystem space utilization.

The filesystem is 6GB, but didn’t have enough space for a 4GB file:

os122:~ # bonnie++ -n 0 -u 0 -f -r 0 -s 4096 -b -d /striped

Using uid:0, gid:0.

Writing intelligently...done

Rewriting...Can't write block.: No space left on device

Bonnie: drastic I/O error (re write(2)): No space left on device

The rest of the space, I assume, was eaten up by btrfs metajunk. During the test, the 4 vCPUs went to 100% and system load reached 4.

top - 17:49:41 up 10 min,  2 users,  load average: 1.71, 0.99, 0.43

Tasks: 123 total,   7 running, 110 sleeping,   6 stopped,   0 zombie

%Cpu(s):  0.7 us, 96.3 sy,  0.0 ni,  0.0 id,  0.0 wa,  0.0 hi,  3.0 si,  0.0 st

KiB Mem:   4057688 total,  3899232 used,   158456 free,       24 buffers

KiB Swap:   562172 total,        0 used,   562172 free,  3619024 cached

  PID USER      PR  NI  VIRT  RES  SHR S  %CPU %MEM    TIME+  COMMAND

1518 root      20   0     0    0    0 R  19.3  0.0   0:05.63 btrfs-endio-wri

1512 root      20   0     0    0    0 R  12.3  0.0   0:07.15 btrfs-submit-1

2157 root      20   0 23088 1452 1220 R  12.3  0.0   0:02.04 bonnie++

2100 root      20   0     0    0    0 R  11.0  0.0   0:05.76 btrfs-worker-2

1510 root      20   0     0    0    0 R  10.3  0.0   0:05.80 btrfs-worker-1

2101 root      20   0     0    0    0 R  10.3  0.0   0:05.73 btrfs-worker-3

2099 root      20   0     0    0    0 S   9.0  0.0   0:05.40 flush-btrfs-2

2102 root      20   0     0    0    0 S   5.3  0.0   0:06.21 btrfs-endio-wri

It would appear Suse got tired of fiddling with btrfs and decided to include it in their production release to get some free troubleshooting from the user community. And this would have been just fine if Suse didn’t claim btrfs was production-ready. Not even close.