Am 05.01.2015 um 21:29 schrieb Mark Nelson:
On 01/05/2015 02:20 PM, Stefan Priebe wrote:
Hi Sage,
Am 05.01.2015 um 20:25 schrieb Sage Weil:
On Mon, 5 Jan 2015, Stefan Priebe wrote:
Am 05.01.2015 um 19:36 schrieb Stefan Priebe:
Hi devs,
while btrfs is now declared as stable ;-) i wanted to retest btrfs on
our production cluster on 2 out of 54 osds. So if they crash it
doesn't
hurt.
While if those OSDs run XFS have spikes of 20MB/s every 4-7s. The same
OSDs after formatting them with btrfs have spikes of 190MB/s every
4-7s.
Why does just another filesystem raises the disk load by a factor of
10?
OK this seems to happen cause ceph is creating every 5s a new
subvolume /
snap. Is this really expected / needed?
You can disable it with
filestore btrfs snap = false
I'm curious how much this drops the load down; originally the
snaps were no more expensive than a regular sync but perhaps this
has changed...
- with XFS the average write is at 9Mb/s
- with btrfs (filestore_btrfs_snap=true) write is at 40Mb/s
- with btrfs (filestore_btrfs_snap=false) write is at 20Mb/s
Is that the average and not the spikes? It looks like before the spikes
were 20MB/s and 190MB/s?
Yes these are average values.
Spikes:
- with XFS the spike write is at 20Mb/s
- with btrfs (filestore_btrfs_snap=true) spike write is 200Mb/s
- with btrfs (filestore_btrfs_snap=false) spike is still 185Mb/s but avg
is 1/2 (20Mb/s) see above
Stefan
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