source: gpfs_3.1_ker2.6.20/lpp/mmfs/samples/mmfs.cfg.sample @ 90

## Sample configuration file 

## Numbers may end with a single letter:
##   k or K meaning 1024
##   m or M meaning 1048576 (1024*1024)
##
## The '#' character is the comment character.  Any parameter 
## modified herein should have any preceding '#' removed.
##

########  Memory / Shared Segment Configuration  ########

## The pagepool is used for I/O buffers.  It is always pinned.
## The allowable range is 4M to 512M (AIX).
## The allowable range is 4M to 1300M (LINUX).
#pagepool 64M

## maxblocksize controls the maximum file system block size allowed.
## File systems with larger block sizes cannot be mounted or created
## unless the value of maxblocksize is increased.
## The allowable range is 16K to 16M
## default: maxblocksize 1M
#maxblocksize 

## Maximum number of files to cache. If the number of concurrently open
## files is bigger, then the number of cached files will exceed this value.
## The allowable range is 1 to 100000
#maxFilesToCache 1000

## The maximum number of stat cache entries.
## The default is 4 times the value of the maxFilesToCache parameter.
## The allowable range is 0 to 10000000
#maxStatCache

########  DMAPI configuration  ########

## The dmapiEventTimeout parameter controls the blocking of file operation
## threads of NFS and DFS, while in the kernel waiting for the handling of
## a DMAPI synchronous event. The parameter value is the maximum time, in
## milliseconds, the thread will block. When this time expires, the file
## operation returns ENOTREADY, and the event continues asynchronously.
## The NFS/DFS server is expected to repeatedly retry the operation, which
## eventually will find the response of the original event and continue.
## This mechanism applies only to read, write and truncate events, and only
## when such events come from NFS and DFS server threads. The timeout value
## is given in milliseconds. The value 0 indicates immediate timeout (fully
## asynchronous event). A value greater or equal 86400000 (which is 24 hours)
## is considered "infinity" (no timeout, fully synchronous event).
## The default value is 86400000.
#dmapiEventTimeout 86400000

## The dmapiSessionFailureTimeout parameter controls the blocking of file
## operation threads, while in the kernel, waiting for the handling of a DMAPI
## synchronous event that is enqueued on a session that has suffered a failure.
## The parameter value is the maximum time, in seconds, the thread will wait
## for the recovery of the failed session. When this time expires and the
## session has not yet recovered, the event is aborted and the file operation
## fails, returning the EIO error. The timeout value is given in full seconds.
## The value 0 indicates immediate timeout (immediate failure of the file
## operation). A value greater or equal 86400 (which is 24 hours) is considered
## "infinity" (no timeout, indefinite blocking until the session recovers).
## The default value is 0.
#dmapiSessionFailureTimeout 0

## The dmapiMountTimeout parameter controls the blocking of mount operations,
## waiting for a disposition for the mount event to be set. This timeout is
## activated at most once on each node, by the first external mount of a
## file system which has DMAPI enabled, and only if there has never before
## been a mount disposition. Any mount operation on this node that starts
## while the timeout period is active will wait for the mount disposition. The
## parameter value is the maximum time, in seconds, that the mount operation
## will wait for a disposition. When this time expires and there is still no
## disposition for the mount event, the mount operation fails, returning the
## EIO error. The timeout value is given in full seconds. The value 0 indicates
## immediate timeout (immediate failure of the mount operation). A value
## greater or equal 86400 (which is 24 hours) is considered "infinity" (no
## timeout, indefinite blocking until the there is a disposition).
## The default value is 60.
#dmapiMountTimeout 60

########  Prefetch tuning ##########

## The value of the 'prefetchThreads' parameter controls the maximum 
## possible number of threads dedicated to prefetching data for 
## files that are read sequentially, or to handle sequential writebehind.  
## The actual degree of parallelism for prefetching is determined
## dynamically in the daemon.  
## (minimum 2, maximum 104)
#prefetchThreads 72

## The 'worker1Threads' parameter controls the maximum number of threads
## that are used to handle other operations associated with data access.
## The primary use is for random read/write requests that cannot be prefetched.
## random IO requests or small file activity.
## (minimum 1, maximum 64)
#worker1Threads 48

## maxMBpS is an estimate of how many MB per sec of data can be transferred
## in or out of a single node. The value is used in calculating the
## amount of IO that can be done to effectively prefetch data for readers
## and/or or write-behind data from writers. The maximum number of IOs in
## progress concurrantly will be 2 * min(nDisks, maxMBpS*avgIOtime/blockSize),
## where nDisks is the number disks that make a filesystem,
## avgIOtime is a measured average of the last 16 full block IO times, and
## blockSize is the block size for a full block in the filesystem (e.g. 256K).
## By lowering this value, you can artificially limit how much IO one node
## can put on all the VSD servers, if there are lots of nodes that
## can overrun a few VSD servers. Setting this too high will usually
## not hurt because of other limiting factors such as the size of the
## pagepool, or the number of prefetchThreads or worker1Threads.
#maxMBpS 150

########  Problem determination Configuration  ########

## Tracing of individual classes of events/operations can be activated by
## adding "trace <trace-class> <trace level>" lines below.
trace all 0

## The 'unmountOnDiskFail' keyword controls how the daemon will respond when
## a disk failure is detected.
##
## When it is set to "no", the daemon will mark the disk as failed and
## continue as long as it can without using the disk. All nodes that are
## using this disk will be notified of the disk failure.  The disk can be
## made active again by using the "mmchdisk" command.  This is the
## suggested setting when metadata and data replication is used because
## the replica can be used until the disk can be brought online again.
##
## When this is set to "yes", any disk failure will cause only the local
## node to panic (force-unmount) the filesystem that contains that disk.
## Other filesystems on this node and other nodes will continue to function
## normally (if they can. The local node can try and remount the filesystem
## when the disk problem has been resolved. This is the suggested setting
## when using VSD disks in large multinode configurations and replication is
## not being used.
##
## When it is set to "meta", the daemon will mark the disk as failed and
## continue as long as it can without using the disk. All nodes that are
## using this disk will be notified of the disk failure.  The disk can be
## made active again by using the "mmchdisk" command.  This is the
## suggested setting when metadata replication is used and there are lots of 
## dataOnly disks because the replica can be used until the disk can be 
## brought online again. The filesystem will remain mounted over dataOnly disk 
## failures, at the expense of user applications getting EIO errors when 
## trying to use disks that have been marked down.
#unmountOnDiskFail no

## The 'dataStructDump' keyword controls whether mmfs will produce a
## formatted dump of its internal data structures into a file named
## internaldump.<daemon pid>.signal whenever it aborts.
## The following entry can either be a directory name in which the file
## will reside, or otherwise a boolean value. When given a positive
## boolean value the directory defaults to /tmp/mmfs.
#dataStructureDump yes

######## Node Override Configuration  ########
##
##   In a multi-node configuration, it may be desirable to configure some
##   nodes differently than others.  This can be accomplished by placing
##   separate, potentially different, copies of the mmfs.cfg file on each
##   node.  However, since maintaining separate copies of the configuration
##   file on each node will likely be more difficult and error prone,
##   the same effect can be achieved via node overrides wherein a single
##   mmfs.cfg file is replicated on every node.
##
##   A node override is introduced by a line containing a node name or list
##   of node names in square brackets.  All parameter specifications
##   that follow will apply only to the listed nodes.  A "[common]" line
##   ends a section of node overrides.  For example the following fragment:
##
##     pagepool 30M
##
##     [tiger5,tiger6]
##     pagepool 10M
##
##     [tiger9]
##     pagepool 64M
##
##     [common]
##     maxFilesToCache 200
##
##   configures the page pool on most nodes as 30 megabytes.  However,
##   on tiger5 and tiger6 the page pool is configured with a smaller
##   page pool of 10 megabytes.  On tiger9 the page pool is configured
##   with a larger page pool of 64 megabytes.  Lines after the "[common]" line
##   again apply to all nodes, i.e. every node will have a maxFilesToCache 
##   of 200.