| Global File System |
| ------------------ |
| |
| http://sources.redhat.com/cluster/ |
| |
| GFS is a cluster file system. It allows a cluster of computers to |
| simultaneously use a block device that is shared between them (with FC, |
| iSCSI, NBD, etc). GFS reads and writes to the block device like a local |
| file system, but also uses a lock module to allow the computers coordinate |
| their I/O so file system consistency is maintained. One of the nifty |
| features of GFS is perfect consistency -- changes made to the file system |
| on one machine show up immediately on all other machines in the cluster. |
| |
| GFS uses interchangable inter-node locking mechanisms. Different lock |
| modules can plug into GFS and each file system selects the appropriate |
| lock module at mount time. Lock modules include: |
| |
| lock_nolock -- allows gfs to be used as a local file system |
| |
| lock_dlm -- uses a distributed lock manager (dlm) for inter-node locking |
| The dlm is found at linux/fs/dlm/ |
| |
| In addition to interfacing with an external locking manager, a gfs lock |
| module is responsible for interacting with external cluster management |
| systems. Lock_dlm depends on user space cluster management systems found |
| at the URL above. |
| |
| To use gfs as a local file system, no external clustering systems are |
| needed, simply: |
| |
| $ mkfs -t gfs2 -p lock_nolock -j 1 /dev/block_device |
| $ mount -t gfs2 /dev/block_device /dir |
| |
| GFS2 is not on-disk compatible with previous versions of GFS. |
| |
| The following man pages can be found at the URL above: |
| gfs2_fsck to repair a filesystem |
| gfs2_grow to expand a filesystem online |
| gfs2_jadd to add journals to a filesystem online |
| gfs2_tool to manipulate, examine and tune a filesystem |
| gfs2_quota to examine and change quota values in a filesystem |
| mount.gfs2 to help mount(8) mount a filesystem |
| mkfs.gfs2 to make a filesystem |