Hitachi AMS 2100, Руководство по оборудованию

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Introduction
1–19
Hitachi AMS 2100/2300 Storage System Hardware Guide
iSCSI interface
The AMS2100/AMS2300 provides 4 iSCSI ports (for the case of the dual
Controller configuration) by installing an optional iSCSI interface board. The
iSCSI interface is capable of operating at data transfer speed of up to 1000
M bytes/s (when the 10G bps iSCSI interface board is installed).
The AMS2100/AMS2300 supports 1G bps or 10G bps iSCSI (1000Base-T).
With the HBA for iSCSI, Generic NIC + Software initiator, and Network
Switch, the AMS2100/AMS2300 subsystem can be located up to 100
meters.
With the 10G bps iSCSI, with 50/125 um multimode (OM3/
0M2) Cable, the AMS2100/AMS2300 subsystem can be located up to
300 (OM3) meters
,
or 82 (OM2) meters.
High capacity cache
The AMS 2100/2300 supports a maximum of 4 GB high capacity cache per
control unit. This cache configuration supports immediate reporting to a
host when data is written from the host to the cache. This is explained in
detail in the next section.
Cache management
The cache management function works as described in the following
process.
1. Data is stored in the cache when reading and writing. It is dynamically
managed depending on the workload read and write I/O characteristics.
The high percent cache hit rate is expected due to the transaction
processing that the data is updated after referencing the data. The
system throughput is increased by the reduced data writing time.
2. As soon as data is written onto the cache, it is reported to the host. The
write operation onto the disk will be asynchronously performed later.
Because the host does not have to wait for the data to be written to a
disk drive, it can perform the next process immediately, significantly
improving system performance.
3. One specified logical unit from the host per controller can be resident in
the cache. The high throughput can be realized for the specified logical
unit since 100% cache percent hit rate is expected when reading from
the host and writing.
4. Optimum segment size can be specified by dividing cache memory into
multiple partitions in accordance with applications, and then cache
memory can be effectively used and tuned according to user system by
occupying cache memory by certain logical units.
NOTE: Even if there is an electric power failure during the write process,
the data is saved because the cache is nonvolatile. For data assurance time,
refer to Table 1-9 on page 1-20 .