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Chapter 7 Thin Provisioning Pool Management
7.2 Functions in the Action Area for Thin Provisioning
ETERNUS Web GUI User’s Guide
Copyright 2013 FUJITSU LIMITED P2X0-1090-10ENZ0
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4 Click the [Done] button to return to the [Thin Provisioning Pool] screen.
End of procedure
7.2.8 Modify Cache Parameters (Thin Provisioning Pool)
This function changes the cache parameters of each Thin Provisioning Pool.
Device performance varies depending on the cache hit ratio. The cache hit ratio can be improved by detecting
the sequentiality for a Read/Write request from the host and reading continuous data in advance. The
characteristics of Read/Write requests from the host depends on the system. Device performance may improve
by specifying a cache parameter that is suitable for the system that is being used.
The following parameter can be specified:
• Multi Writeback Count (MWC)
Specify the number of processes that can be written back at the same time.
The procedure to modify cache parameters is as follows:
Procedure
1 Select which TPP to change the cache parameters for (multiple selections can be made) and
click [Modify Cache Parameters] in [Action].
2 Change the cache parameters and click the [Modify] button.
• Multi Writeback Count (MWC)
Specify the Multi Writeback Count.
When specifying a larger "Multi Writeback Count" value, sequential write access performance is
improved. Note that this is not effective when a number of random write accesses occur. Depending
on the ratio of read access and write access, read access performance may be reduced.
If pinned data exists in the ETERNUS DX Disk storage system, MWC cannot be configured.
• The same cache parameter can be applied for multiple TPPs in a single operation.
• Cache parameters other than MWC are specified for each TPV. Refer to "5.2.18 Modify Cache Parameters"
(page 148) for details.
The setting values that are available for Multi Writeback Count vary depending on the RAID type
and drive configuration. Refer to "E.2 Input Conditions for MWC" (page 1007)
for details.