DVS periodic sync makes the DVS
closesync
mount option redundant. Periodic sync is more efficient than
closesync
because it is aware of which files may have dirty pages.
Use the following three
/proc
files to tune DVS periodic sync behavior (
echo
desired value into each file):
/proc/fs/dvs/sync_num_threads
Specifies the number of threads on the DVS server that
perform sync operations. There must be at least 1 thread and
the maximum number is 32. The default value is 8.
/proc/fs/dvs/sync_dirty_timeout_secs
On DVS servers, specifies the number of seconds that must
have passed since the file was written before DVS syncs it.
The default value is 300. The objective is to reduce
unnecessary sync operations for files actively being updated.
Decreasing this number increases the likelihood that the file is
in use when it is synced. Increasing this number increases the
likelihood that processes are killed during a server failure.
On DVS clients, specifies the number of seconds that must
have passed since the file was written before DVS asks the
server for an updated sync time. The default value is 300.
Decreasing this number increases the number of DVS
requests being sent. Increasing this number increases the
likelihood that processes are killed during a server failure.
/proc/fs/dvs/sync_period_secs
On DVS servers, specifies the number of seconds before the
sync_num_threads
syncs files on the DVS server (if
necessary). The default value is 300.
On DVS clients, specifies the number of seconds between
checks for dirty files that need to request the last sync time
from the server. The default value is 600.
A fourth
/proc
file,
/procsfs/dvs/sync_stats
, collects statistics of the syncing behavior. This setting is not
tunable (read only).
6.1.6.3 About DVS Statistics
The
/proc/fs/dvs/stats
file contains statistics for system operations that cannot be correlated to a specific
DVS mount point, and is thus most interesting on DVS servers.
The same type of information is also available on DVS clients at the mount point
(
/proc/fs/dvs/mounts/0/stats
,
/proc/fs/dvs/mounts/1/stats
, etc.) Each of these files contains the
statistics for that specific mount point only. More information about each of these mount points can be obtained by
viewing the mount file that resides in the same directory (e.g.,
/proc/fs/dvs/mounts/0/mount
).
●
The first section of the file contains remote procedure call (RPC) message-passing statistics. Each line
displays a file system operation, followed by counts of successful and failed send operations of that type,
counts of successful and failed receive operations of that type, the time it took to process the most recent
operation of that type, and the maximum time to process that operation in the history of the system.
●
The second section of the file contains statistics on virtual file system (VFS) operations. Each line displays a
callback name, followed by counts of successful and failed callbacks of that name, the time it took to process
the most recent callback of that name, and the maximum time to process that callback in the history of the
system.
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