Veritas File System 5.0 Release Notes (September 2006)

Veritas File System 5.0 Release Notes
New Features
Chapter 112
NOTE CDS feature is not available with Base-VxFS and HP OnlineJFS bundles.To enable the
CDS feature, an additional license is required.
• Concurrent I/O
Concurrent I/O (VX_CONCURRENT) allows multiple processes to read or write to the same file
withoutblocking other read () or write () calls. POSIX semantics requires read() and write()
calls to be serialized on a file with other read() and write() calls. With POSIX semantics, a read
either reads the data before or after the write occurred. With the VX_CONCURRENT advisory set to on,
the read and write operations are not serialized as in the case of a character device. This advisory is
generally used by applications that require high performance for accessing data and do not perform
overlapping writes to the same file. It is the responsibility of the application or the running threads to
coordinate write activities to thesame file when using Concurrent I/O.
Concurrent I/O can be enabled in two ways:
— Concurrent I/O can be set through the file descriptor and ioctl() operation using the VX_SETCACHE
ioctl command with the VX_CONCURRENT advisory flag. Only the read () and write () calls
occurring through this file descriptor use concurrent I/O. The read and write operations occurring
through other file descriptors will still follow the POSIX semantics. See vxfsio (7) manpage for
more details.
— Concurrent I/O can be enabled on all files in the file system by mounting with the cio mount option.
The read and write operations occurring on all the files in this particular file system will use
concurrent I/O. See mount_vxfs (1M) manpage for more details.
NOTE Concurrent I/O is not available with Base-VxFS and OnlineJFS. To enable the
Concurrent I/O feature an additional license is required.
• Nested mount support
This feature allows mounting of a VxFS file system on any of the VxFS mount points. A directory on a
shared VxFS file system may be used as a mount point for a VxFS file system, enabling nested mounts
of shared file systems.
NOTE Shared file systems cannot be mounted with OnlineJFS and Base-VxFS licenses. To
enable nested mounts on shared file systems, an additional license is required.
• Multi-volume file system availability