In contrast, after a write, the new data is uncompressed on disk. See About compressing files. VxFS provides online data backup using the snapshot feature. An image of a mounted file system instantly becomes an exact read-only copy of the file system at a specific point in time. The original file system is called the snapped file system, while the copy is called the snapshot.
When changes are made to the snapped file system, the old data is copied to the snapshot. When the snapshot is read, data that has not changed is read from the snapped file system, changed data is read from the snapshot. Copying selected files from the snapshot file system using find and cpio. Backing up the entire file system using fscat. Initiating a full or incremental backup using vxdump. See About snapshot file systems.
A FileSnap is a space-optimized copy of a file in the same name space, stored in the same file system. Freezing a file system is a necessary step for obtaining a stable and consistent image of the file system at the volume level.
Consistent volume-level file system images can be obtained and used with a file system snapshot tool. Synchronizing operations, which require freezing and thawing file systems, are done on a cluster-wide basis. See Freezing and thawing a file system.
VxFS provides superior performance for synchronous write applications. The mount -o datainlog option greatly improves the performance of small synchronous writes. See the fcntl 2 manual page. Added support for more than 64K sub-directories. If maxlink is disabled on a file system, the sub-directory limit will be 32K by default. To enable the maxlink option at mkfs time. For example:. To disable the maxlink option at mkfs time. To enable the maxlink option through the fsadm command on a mounted files system.
To disable the maxlink option through the fsadm command on a mounted file system. You can use the mmap function to establish shared memory mapping. See the mmap 2 manual page. The multi-volume file system MVFS feature allows several volumes to be represented by a single logical object. You can create a single VxFS file system on this multi-volume set. This feature can be used only in conjunction with VxVM.
See About multi-volume file systems. You can use a directory on a cluster mounted or local mounted file system as a mount point for a local file system or another cluster file system. You export the NFS file systems from the cluster. Parallel threads that access a large volume and perform access and updates on a directory that commonly exist in a file system, suffer from an exponentially longer wait time for the threads.
This feature creates partitioned directories to improve the directory performance of file systems. When any directory crosses the tunable threshold, this feature takes an exclusive lock on the directory inode and redistributes the entries into various respective hash directories. These hash directories are not visible in the name-space view of the user or operating system. For every new create, delete, or lookup thread, this feature performs a lookup for the respective hashed directory depending on the target name and performs the operation in that directory.
This leaves the parent directory inode and its other hash directories unobstructed for access, which vastly improves file system performance. This feature operates only on disk layout Version 8 or later file systems. VxFS supports quotas, which allocate per-user and per-group quotas and limit the use of two principal resources: files and data blocks.
You can assign quotas for each of these resources. Each quota consists of two limits for each resource: hard limit and soft limit. The quotacheck command is an exception - VxFS does not support an equivalent command. See About quota checking with Veritas File System. Quota support for various file systems is implemented using the generic code provided by the Linux kernel.
However, VxFS does not use this generic interface. VxFS supports the following quota-related commands:. See About snapshot file systems. A FileSnap is a space-optimized copy of a file in the same name space, stored in the same file system. Freezing a file system is a necessary step for obtaining a stable and consistent image of the file system at the volume level. Consistent volume-level file system images can be obtained and used with a file system snapshot tool.
See Freezing and thawing a file system. VxFS provides superior performance for synchronous write applications. The mount -o datainlog option greatly improves the performance of small synchronous writes. Added support for more than 64K sub-directories. If maxlink is disabled on a file system, the sub-directory limit will be 32K by default. To enable the maxlink option at mkfs time. For example:. To disable the maxlink option at mkfs time.
To enable the maxlink option through the fsadm command on a mounted files system. To disable the maxlink option through the fsadm command on a mounted file system. The multi-volume file system MVFS feature allows several volumes to be represented by a single logical object. You can create a single VxFS file system on this multi-volume set. This feature can be used only in conjunction with VxVM. See About multi-volume file systems. Parallel threads that access a large volume and perform access and updates on a directory that commonly exist in a file system, suffer from an exponentially longer wait time for the threads.
This feature creates partitioned directories to improve the directory performance of file systems. When any directory crosses the tunable threshold, this feature takes an exclusive lock on the directory inode and redistributes the entries into various respective hash directories.
These hash directories are not visible in the name-space view of the user or operating system. For every new create, delete, or lookup thread, this feature performs a lookup for the respective hashed directory depending on the target name and performs the operation in that directory.
This leaves the parent directory inode and its other hash directories unobstructed for access, which vastly improves file system performance. This feature operates only on disk layout Version 8 or later file systems. VxFS supports quotas, which allocate per-user and per-group quotas and limit the use of two principal resources: files and data blocks.
You can assign quotas for each of these resources. Each quota consists of two limits for each resource: hard limit and soft limit. The hard limit represents an absolute limit on data blocks or files. A user can never exceed the hard limit under any circumstances.
The soft limit is lower than the hard limit and can be exceeded for a limited amount of time. This allows users to exceed limits temporarily as long as they fall under those limits before the allotted time expires. See About Veritas File System quota limits. The reverse path name lookup feature obtains the full path name of a file or directory from the inode number of that file or directory. The reverse path name lookup feature can be useful for a variety of applications, such as for clients of the VxFS File Change Log feature, in backup and restore utilities, and for replication products.
Typically, these applications store information by inode numbers because a path name for a file or directory can be very long, thus the need for an easy method of obtaining a path name. See About reverse path name lookup. SmartIO uses advanced, customizable heuristics to determine what data to cache and how that data gets removed from the cache. SmartIO uses a cache area on the target device or devices. The cache area is the storage space that SmartIO uses to store the cached data and the metadata about the cached data.
The SmartTier option is built on a multi-volume file system. Using SmartTier, you can map more than one volume to a single file system.
You can then configure policies that automatically relocate files from one volume to another, or relocate files by running file relocation commands.
Having multiple volumes lets you determine where files are located, which can improve performance for applications that access specific types of files.
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