Veritas File System 5.1 SP1 Administrator"s Guide (5900-1499, April 2011)

■ Separating metadata from file data.
■ Encapsulating volumes so that a volume appears in the file system as a file.
This is particularly useful for databases that are running on raw volumes.
■ Guaranteeing that a dataonly volume being unavailable does not cause a
metadataok volume to be unavailable.
To use the multi-volume file system features, Veritas Volume Manager must be
installed and the volume set feature must be accessible. The volume set feature
is separately licensed.
Volume availability
MVS guarantees that a dataonly volume being unavailable does not cause a
metadataok volume to be unavailable. This allows you to mount a multi-volume
file system even if one or more component dataonly volumes are missing.
The volumes are separated by whether metadata is allowed on the volume. An
I/O error on a dataonly volume does not affect access to any other volumes. All
VxFS operations that do not access the missing dataonly volume function
normally.
Some VxFS operations that do not access the missing dataonly volume and
function normally include the following:
■ Mounting the multi-volume file system, regardless if the file system is read-only
or read/write.
■ Kernel operations.
■ Performing a fsck replay. Logged writes are converted to normal writes if the
corresponding volume is dataonly.
■ Performing a full fsck.
■ Using all other commands that do not access data on a missing volume.
Some operations that could fail if a dataonly volume is missing include:
■ Reading or writing file data if the file's data extents were allocated from the
missing dataonly volume.
■ Using the vxdump command.
Volume availability is supported only on a file system with disk layout Version 7
or later.
91Multi-volume file systems
Features implemented using multi-volume support