US Robotics 7931 Podręcznik Użytkownika Pobierz pdf (Strona 171)

Chapter 5 Staging 147

Example 4: Complex Prioritization

Assume that there are two Sun StorageTek SAM file systems with the following

requirements:

■ No request should sit too long in the queue (age_priority).

■ When one of the file systems is below the LWM, staging requests should take

precedence.

■ When one of the file systems is above the LWM but below the HWM, it is not

necessary to prioritize archive or stage requests one over the other.

CODE EXAMPLE 5-5 shows the affected directives.

The other directives remain unchanged.

When one of the file systems goes over the HWM, archive requests take priority.

Suppose that both file systems are over the HWM and it is more important to

prevent the second file system (for example, samfs2) from filling up. This might

occur if, for example, samfs1 is a user working file system and samfs2 is the

critical-system file system.

CODE EXAMPLE 5-6 shows a preview.cmd file that prioritizes requests according to

the requirements in the preceding list.

CODE EXAMPLE 5-5 Directives

lwm_priority = -200.0

lhwm_priority = 0.0

hlwm_priority = 0.0

CODE EXAMPLE 5-6 A preview.cmd File Showing Complex Prioritization

age_priority = 100.0

vsn_priority = 20000.0

lhwm_priority = -200.0

hlwm_priority = -200.0

fs = samfs1

hwm_priority = 1000.0

fs = samfs2

hwm_priority = 5000.0

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US Robotics 7931 Podręcznik Użytkownika Strona 171