Am 17.10.2011 11:40, schrieb Christian Brunner:
2011/10/15 Martin Mailand<martin@xxxxxxxxxxxx>:
Hi Christian,
I have a very similar experience, I also used josef's tree and btrfs snaps =
0, the next problem I had than was excessive fragmentation, so I used this
patch http://marc.info/?l=linux-btrfs&m=131495014823121&w=2, and changed the
btrfs option to (btrfs options = noatime,nodatacow,autodefrag) that kept the
fragmentation under control.
But even with this setup after a few days the load on the osd is unbearable.
How did you find out about our fragmentation issues? Was it just a
performance problem?
I used filefrag to show the number of extents, after the patch, I have
on average 1,14 extents per 4MB ceph object on the osd.
As far as I understood the doku if you disable the btrfs snapshot
functionality the writeahead journal is activated.
http://ceph.newdream.net/wiki/Ceph.conf
And I get this in the logs.
mount: enabling WRITEAHEAD journal mode: 'filestore btrfs snap' mode is not
enabled
May I asked what kind of probs you did have with ext4? Because I am looking
into this direction as well.
You can read about our ext4 problems here:
http://marc.info/?l=ceph-devel&m=131201869703245&w=2
I still can reproduce the bug with v3.1-rc9.
Our bugreport with RedHat didn't make any progress for a long time,
but last week RedHat made two sugestions:
- If you configure ceph with 'filestore flusher = false', do you see
any different behavior?
- If you mount with -o noauto_da_alloc does it change anything?
Since I have just migrated to btrfs, I've some problems to check this,
but I'll try to do this as soon as I can get hold of some extra
hardware.
I can check this, I have a spare cluster at the moment.
Regards,
Christian
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