Ceph

Copy-paste from recent ceph-devel email from Sam:

filestore [min|max] sync interval:

Periodically, the filestore needs to quiesce writes and do a syncfs in
order to create
a consistent commit point up to which it can free journal entries. Syncing more
frequently tends to reduce the time required to do the sync, and
reduces the amount
of data that needs to remain in the journal. Less frequent syncs
would allow the
backing filesystem to better coalesce small writes and metadata
updates hopefully
resulting in more efficient syncs. 'filestore max sync interval'
defines the maximum
time period between syncs, 'filestore min sync interval' defines the
minimum time
period between syncs.

filestore flusher:

The filestore flusher forces data from large writes to be written out
using sync_file_range
before the sync in order to (hopefully) reduce the cost of the
eventual sync. In practice,
disabling 'filestore flusher' seems to improve performance in some cases.

filestore queue max ops:

'filestore queue max ops' defines the number of in progress ops the
filestore will accept
before blocking on queueing new ones. This mostly shouldn't have much
of an effect
on performance and should probably be ignored.

filestore op threads:

'filestore op threads' defines the number of threads used to submit
filesystem operations
in parallel.

journal dio:

'journal dio' enables using O_DIRECT for writing to the journal. This
should usually
be enabled. If possible, 'journal aio' should also be enabled to
allow use of libaio
to do asynchronous writes.

osd op threads:

'osd op threads' defines the size of the thread pool used to service
OSD operations
such as client requests. Increasing this may increase the rate of
request processing.

osd disk threads:

'osd disk threads' defines the number of threads used to perform background disk
intensive osd operations such as scrubbing and snap trimming.