Seagate ST39175LW Anleitung zur Fehlerbehebung PDF herunterladen (Seite 34)

Processing Before and After the Frozen Image

20 NetBackup ServerFree Agent System Administrator’s Guide

Dialog for Quiesce/Unquiesce

Quiescing the Stack

The storage management stack is a layered arrangement of software elements. An I/O

request originated by a database application passes from element to element until a

hardware request to move data reaches the storage network. Each stack element performs

a variety of functions, some of which treat I/O requests like transactions to assure their

completion. Before a frozen image is created, therefore, the stack must be quiesced (made

transactionally consistent).

Since the file system is the front-line interface to applications for managing files and

performing I/O, file system quiesce is a critical part of quiescing the stack.

File System

Two of the principal tasks of quiescing the file system are the following:

◆ Prohibit new I/O requests from initiating, which is called locking the file system.

◆ Flush file system cache (write cached data back to disk). The system must complete

any outstanding application I/O and note completion of outstanding metadata

updates.

Frozen Image Consumer

(NetBackup)

Database Application

Quiesce stack,

trigger frozen image.

Finish transactions.

Out of quiesce mode.

Continue processing.

Quiesce.

Quiesce acknowledge.

Unquiesce.

... In quiesce mode ....

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Seagate ST39175LW Anleitung zur Fehlerbehebung Seite 34