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118 Sun StorageTek SAM Archive Configuration and Administration Guide • Version 4, Update 6, 04/07

About Partial Releasing and Partial

Staging

Releasing and staging are complementary processes. Files can be completely

released from online disk cache after they are archived, or a site can specify that the

beginning of a file (the stub) remain in disk cache while the remainder of the file is

released. Partially releasing a file provides immediate access to data in the file stub

without requiring that the file be staged first.

As system administrator, you can specify both the default partial release size and the

maximum size of the stub to remain online when a file system is mounted. You can

set these through the mount(1M) command or in the File System Manager software.

See the File System Manager online help for more information.

The mount(1M) command options are as follows:

■ -o partial=n option – Sets the default size (n) of a file stub to remain online.

The -o partial=n setting must be less than or equal to the -o maxpartial=n

setting.

■ -o maxpartial=n option – Sets the maximum size (n) of a file stub to remain

online.

You can specify the default stub size for a file by specifying the -p option on the

release(1) command or the p option on the sam_release(3) library routine. To

specify different-sized file stubs for different types of files or different applications, a

user can specify the –s option on the release(1) command or the s option on the

sam_release(3) library routine. The -s and s values must be less than the

-o maxpartial value used with the mount(1M) command when the file system

was mounted.

Note – Even when the file is partially released, it still takes up space on the disk

equal to one DAU. For example, if the partial release file stub is set to 16K and the

DAU size is 256K, the actual space consumed by the file on the disk is 256K, even

though the file has been partially released.

Another mount option, -o partial_stage=n, allows a system administrator to

establish how much of a partial release stub must be read before the rest of the file is

staged. Reading past the -o partial_stage=n size specification initiates the stage

of the file.

By default, the -o partial_stage=n option is set to the size of the partial release

stub. Changing this value affects file staging as follows:

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