US Robotics 7931 Betriebsanweisung PDF herunterladen (Seite 26)

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

files in a Sun StorageTek SAM file system and writes the archive copy to archive

media. You can configure the archiver to create up to four archive copies on a

variety of archive media. If a file is segmented, each segment is treated as a file

and is archived separately. The archiving process is initiated after disk-based files

match a site-definable set of selection criteria.

For more information about the archiver, see “Archiving” on page 33. For more

information about segmented files, see “Using Segmented Files” on page 222.

■ The releaser automatically maintains the file system’s online disk cache at site-

specified percentage usage thresholds by freeing disk blocks occupied by eligible

archived files.

Releasing is the process of freeing primary (disk) storage that is used by an

archived file’s data. Two threshold values, the high-water mark and the low-

water mark, both expressed as a percentage of total disk space, are used to

manage online disk cache free space. When online disk consumption exceeds the

high-water mark, the system automatically begins releasing the disk space

occupied by eligible archived files. Disk space occupied by archived file data is

released until the low-water mark is reached. Files are selected for release

depending on their size and age. The first portion of a file can be retained on disk

for speedy access and for masking staging delays. If a file has been archived in

segments, portions of the file can be released individually. For more information

about the releaser, see “Releasing” on page 115.

■ The stager restores file data to the disk cache. When a user or process requests file

data that has been released from disk cache, the stager automatically copies the

file data back to the online disk cache.

When a file whose data blocks have been released is accessed, the stager

automatically stages the file or file segment data back to online disk cache. The

read operation tracks along directly behind the staging operation, allowing the

file to be immediately available to an application before the entire file is

completely staged.

The Sun StorageTek SAM software processes stage request errors automatically. If

a stage error is returned, the system attempts to find the next available archive

copy of the file. Stage errors that can be automatically processed include media

errors, unavailability of media, unavailability of an automated library, and others.

For more information about staging, see “Staging” on page 133.

■ Τhe recycler clears archive volumes of expired archive copies and makes volumes

available for reuse.

As users modify files, archive copies associated with the old versions of these files

are considered to be expired on their archive media. Such copies are no longer

needed, so they can be purged from the system. The recycler identifies the archive

volumes with the largest proportions of expired archive copies and preserves the

unexpired copies by moving them to separate volumes.

If a removable media volume contains only expired copies, you can take one of

the following actions:

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