Modify Cache Parameters - Fujitsu ETERNUS DX60 S3 User Manual

Chapter 3 Volume Management

3.14 Modify Cache Parameters

3.14

Modify Cache Parameters

This function changes the cache parameters of each volume.
Performance of the storage system varies depending on the cache hit rate. The ETERNUS DX detects
sequentiality when a host requests Read/Write. If sequentiality is detected when a Read request is issued, the
cache hit rate is improved by reading the sequential data into the cache memory in advance. The
characteristics of Read/Write requests from the host depends on the system. Performance of the storage
system may improve by specifying a cache parameter that is suitable for the system that is being used.
The following parameters can be specified:
• Cache Page Capacity
Specify the cache capacity that is used by volumes.
• Prefetch Limit (PL)
Specify the value to calculate the amount of data that is to be read from the drive in advance (amount of
data to prefetch from the disk) when the cache detects the sequentiality of data access (Read IO).
• Force Prefetch Mode (FP)
Specify whether to perform prefetch even if the sequentiality of data access (Read IO) is not detected.
• Multi Writeback Count (MWC)
Specify the number of processes that can be written back at the same time.
• Prefetch Sequential Detect Count (PSDC)
Specify the number of times for sequential data detection to determine the sequentiality of data access
(Read IO).
• Sequential Dirty Detect Count (SDDC)
Specify the number of times for sequential data detection to determine the sequentiality of data access
(Write I/O).
• Sequential Slope (SS)
A parameter to determine the sequentiality of data access (Read I/O). Specify the number of LBAs by which
the previous I/O and the current I/O are considered as sequential data.
• Sequential Dirty Slope (SDS)
A parameter to determine the sequentiality of data access (Write I/O). Specify the number of LBAs by which
the previous I/O and the current I/O are considered as sequential data.
• Sequential Parallel Multi I/O Count (SPMC)
A parameter to determine the sequentiality of data access (Read I/O and Write I/O). Specify the number of
I/Os by which the previous I/O and the current I/O are considered as sequential data.
• Extreme Cache Pool
Specify whether to "Enable" or "Disable" EXCP for the volumes.
• For TPVs, specify the MWC for each TPP. Refer to
(page 582)
• Cache parameters cannot be changed when pinned data exists in the ETERNUS DX.
The same cache parameter can be applied for multiple volumes in a single operation.
for details.
ETERNUS Web GUI User's Guide (Settings)
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"6.9 Modify Cache Parameters (Thin Provisioning Pool)"
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