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5.3
Cache Management
Cache management features include the following:
Data is stored in cache when reading and writing; it is dynamically managed, depending
on the workload read and write I/O characteristics. A high percent cache hit rate is
expected, due to transaction processing (data is updated after it is referenced). System
throughput is increased by the reduced data writing time.
Writing completion is reported to the host at the same time the data is written onto the
cache; the write operation onto the disk will be asynchronously performed later. The
host can perform the next process without waiting for the write operation onto disk.
The data written onto the cache is saved in the event of an electric power failure due to
the nonvolatile cache. The data is assured for 24 hours on the full charge of a standard
configuration.
One specified logical unit on each controller can be resident in cache. High throughput
can be realized for the specified logical unit since a 100% cache percent hit rate is
expected when reading and writing from the host.
Cache specifications are shown in the following tables:
Table 5.3
Rack-Mount Model Cache Specifications
Item
Cache
specifications
Note: LRU is an abbreviation for Least Recently Used.
Note: For information about the global rack-mount model, refer to the Acer | HDS AMS200
and WMS100 Global Global 19-Inch Rack Reference Guide.
Table 5.4
Floor Model Cache Specifications
Item
Cache
specifications
Note: LRU is an abbreviation for Least Recently Used.
98
Chapter 5 Functional and Operational Characteristics
Model
RKS
Capacity (M bytes/CTL)
1,024 to 2,048
Control method
Read LRU (Note) /Write after
Battery backup
Provided
Backup duration (h)
24 (When cache of 2,048 M
bytes/CTL is installed)
Model
Floor (RKS+H1J) Model
Capacity (M bytes/CTL)
1,024 to 2,048
Control method
Read LRU/Write after (see Note)
Battery backup
Provided
Backup duration (h)
24 (When cache of 2,048 M bytes/CTL is installed)
Rack-Mount Model
RKAJ
-
-
-
-
Floor Model
Floor (RKS+RKAJ+H2J) Model
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