Acer HDS WMS100, Reference Manual

Page: 106 / 328

84 Chapter 5 Functional and Operational Characteristics
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.
„
Optimum segment size can be specified by dividing cache memory into multiple
partitions in accordance with applications. Then cache memory can be effectively used
and tuned according to the user system by occupying cache memory by certain logical
units.
Cache specifications are shown in the following tables:
Table 5.3 Rack-Mount Model Cache Specifications
Rack-Mount Model Item Model
RKXS RKAJAT
Capacity (M bytes/CTL) 512/1,024 -
Control method Read LRU ( Note ) /Write after -
Battery backup Provided -
Cache
specifications
Backup duration (h) 24 (When cache of 1,024 M
bytes/CTL is installed)
-
Note: LRU is an abbreviation for Least Recently Used.
Note: For information about the global rack-mount model, refer to the Acer | HDS Global
19-Inch Rack Reference Guide.