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

Veritas File System I/O

This chapter includes the following topics:

■ About Veritas File System I/O

■ Buffered and Direct I/O

■ Concurrent I/O

■ Cache advisories

■ Freezing and thawing a file system

■ Getting the I/O size

■ Enabling and disabling Concurrent I/O for a DB2 database

About Veritas File System I/O

VxFS processes two basic types of file system I/O:

■ Sequential

■ Random or I/O that is not sequential

For sequential I/O, VxFS employs a read-ahead policy by default when the

application is reading data. For writing, it allocates contiguous blocks if possible.

In most cases, VxFS handles I/O that is sequential through buffered I/O. VxFS

handles random or nonsequential I/O using direct I/O without buffering.

VxFS provides a set of I/O cache advisories for use when accessing files.

See the vxfsio(7) manual page.

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