HP ProLiant DL380G5-WSS 3.7.0 HP StorageWorks HP Scalable NAS File Serving Sof - Page 122
Journaling filesystem, Server registry, Filesystem management and integrity
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Journaling filesystem When you initiate certain filesystem operations such as creating, opening, or moving a file or modifying its size, the filesystem writes the metadata, or structural information, for that event to a transaction journal. The filesystem then performs the operation. If a server using the filesystem should crash during an operation, the journal is replayed and any journaled operations in progress at the time of the crash are completed. This procedure ensures that the structure of the filesystem is consistent. Users on other servers will experience only a slight delay in filesystem operations during the recovery. Server registry HP Scalable NAS uses a registry to control server access to PSFS filesystems on the SAN disks imported into the cluster. A server is added to the registry when it mounts its first PSFS filesystem. Under normal operations, a server remains in the registry until it either unmounts its last PSFS filesystem or leaves the cluster. However, if a server crashes or loses communication with the cluster and that server is in the registry (indicating that it had active PSFS mounts), HP Scalable NAS will remove the server's access to the filesystems. When this situation occurs, an alert will appear on the Management Console and a message will be written to the cluster log. You will need to reboot the server to restore its access. After the server is rebooted and rejoins the cluster, it is deleted from the registry. When the server again mounts a PSFS filesystem, it will be added back into the registry. Filesystem management and integrity HP Scalable NAS uses the SANPulse daemon to manage PSFS filesystems. SANPulse performs the following tasks: • Coordinates filesystem mounts, unmounts, and crash recovery operations. • Checks for cluster partitioning, which can occur when cluster network communic- ations are lost but the affected servers can still access the SAN. If this situation occurs, HP Scalable NAS determines which servers should continue to have SAN access and excludes the other servers from the SAN. This step prevents data corruption from occurring. • Communicates filesystem status to the Management Console. It reports both the global status of a filesystem (for example, whether it is up or going through a 122 Configure PSFS filesystems