IBM General Parallel File System for AIX: Data Management API Guide

GPFS configuration options for DMAPI

The GPFS configuration file mmfs.cfg, located in directory /var/mmfs/etc, includes several options for DMAPI which define various time-out intervals. The file mmfs.cfg.sample that is installed in directory /usr/lpp/mmfs/samples contains a sample configuration. See the GPFS for AIX: Guide and Reference for more information on the mmconfig command.

Following are the DMAPI configuration options:

dmapiEventTimeout

The dmapiEventTimeout option 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. See also "Support for DFS and NFS".

dmapiSessionFailureTimeout

The dmapiSessionFailureTimeout option 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. See also Chapter 5, "Failure and recovery of Data Management API for GPFS" for details on session failure and recovery.

dmapiMountTimeout

The dmapiMountTimeout option 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 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 still is 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 to 86400 (which is 24 hours) is considered "infinity" (no timeout, indefinite blocking until there is a disposition). The default value is 60. See also "Mount and unmount" and "Initializing the Data Management application".