VxFS Functionality on Cluster File Systems
The VERITAS Cluster File System is based on the VERITAS File System (VxFS). Most of the major features of VxFS local file systems are available on cluster file systems, including:
- Extent based space management that maps files up to a terabyte in size.
- Fast recovery from system crashes using the intent log to track recent file system metadata updates.
- Online administration that allows file systems to be extended and defragmented while they are in use.
The following is a list of features and commands that operate on CFS. Every VxFS online manual page has a section on Cluster File System Issues with information on whether the command functions on a cluster-mounted file system and indicates any difference in behavior from local mounted file systems. You can also review the VERITAS Storage Foundation Cluster File System Release Notes for information on the latest CFS features.
Supported Features
| Features and Commands Supported on CFS
|
|---|
| Quick I/O
|
The Quick I/O for Databases feature, using clusterized Oracle Disk Manager (ODM), is supported on CFS. Quick I/O is licensable only through VERITAS Database Editions products.
|
| Storage Checkpoints
|
Storage Checkpoints are supported on cluster file systems, but are licensed only with other VERITAS products.
|
| Snapshots
|
Snapshots are supported on cluster file systems.
|
| Quotas
|
Quotas are supported on cluster file systems.
|
| NFS mounts
|
You can mount cluster file systems to NFS.
|
| Freeze and thaw
|
Synchronizing operations, which require freezing and thawing file systems, are done on a cluster-wide basis.
|
| Memory mapping
|
Shared memory mapping established by the mmap() function is supported on CFS. See the mmap(2) manual page for more information on mapping memory pages.
|
| Disk layout versions
|
CFS supports only disk layout Version 4, 5 or 6. Cluster mounted file systems cannot be upgraded, but a local mounted file system can be upgraded, unmounted, and mounted again as part of a cluster. Use the fstyp –v special_device command to ascertain the disk layout version of a VxFS file system. Use the vxupgrade command to update the disk layout version.
|
| Locking
|
Advisory file and record locking are supported on CFS. For the F_GETLK command, if there is a process holding a conflicting lock, the l_pid field returns the process ID of the process holding the conflicting lock. The nodeid-to-node name translation can be done by examining the /etc/llthosts file or with the fsclustadm command. Mandatory locking, and deadlock detection supported by traditional fcntl locks, are not supported on CFS. See the fcntl(2) manual page for more information on record and file locking.
|
Unsupported Features
Functionality described as not supported may not be expressly prevented from operating on cluster file systems, but the actual behavior is indeterminate. It is not advisable to use unsupported functionality on CFS, or to alternate mounting file systems with these options as local and cluster mounts.
| Features and Commands Not Supported on CFS
|
|---|
Swap files
|
Swap files are not supported on cluster mounted file system.
|
Nested Mounts
|
You cannot use a directory on a cluster mounted file system as a mount point for a local file system or another cluster file system.
|
The mknod command
|
You cannot use the mknod command to create devices on a cluster mounted file system.
|
Cache advisories
|
Cache advisories are set with the mount command on individual file systems, but are not propagated to other nodes of a cluster.
|
Cached Quick I/O
|
This Quick I/O for Databases feature that caches data in the file system cache is not supported.
|
Commands that depend on file access times
|
File access times may appear different across nodes because the atime file attribute is not closely synchronized in a cluster file system. So utilities that depend on checking access times may not function reliably.
|
|
