HP XP P9500 Storage - Manual (Page 24)

Residency operation, see the HP P9000 Performance for Open and Mainframe Systems User
Guide.
NOTE: When you set the cache mode, note the following:
•
Data that is not written by the host (for example, data written by Business Copy) is
asynchronously destaged to the external storage system regardless of the Cache Mode setting.
•
If you set the emulation type for a mainframe system (such as 3390-x), data that is written by
a host using a command such as Format Write is asynchronously destaged to the external
storage system regardless of the Cache Mode setting. Data that is written by a host using a
command such as Update Write is destaged to the external storage system as configured in
the Cache Mode setting.
Inflow control (Enable or Disable)
Inflow control specifies whether the write operation to the cache memory is stopped (Enable) or
continued (Disable) when the write operation to the external volume is impossible. By default,
inflow control is set to Disable.
•
If you select Enable, the writing operation to cache is stopped and the I/O from the host is
not accepted when the writing operation to the external volume is impossible.
•
If you select Disable, the I/O from the host during the retry operation is written to the cache
memory even after the writing operation to the external volume is impossible. Once the writing
operation to the external volume becomes normal, all the data in the cache memory is written
to the external volume (all the data is destaged).
CLPR
When the cache memory is partitioned using Cache Partition, configure a cache logical partition
(CLPR) to access the mapped volume. HP strongly recommends that you place External Storage
array groups in a CLPR other than CLPR0. See the HP P9000 Cache Partition User Guide for the
detailed information on CLPR.
External paths
An external path is a route from a local storage system port to an external storage system port. To
prepare for possible failures of the cable, the switch, or the channel processor, it is recommended
that you create redundant external paths. This redundancy allows you to continue performing the
I/O operations to the external volumes while paths are maintained. You can set up to eight paths.
If two or more external volumes use the same redundant external paths, these external volumes
can be made into a group. This group is called a "path group." In redundant external paths, the
external path that has the highest priority is called the primary path. The external paths other than
priority path are called alternate paths.
Setting of the path groups
A path group is automatically set when you map an external volume or when you change a path
group by using spreadsheets. You cannot set a new path group by itself.
For more information about changing a path group by using spreadsheets, see the HP P9000
Spreadsheet Guide.
Setting of external paths
Use fibre cables to establish multiple paths between the external storage system and the local
storage system. At this time, connect to the external storage system from the different cluster port
of the local storage system.
If multiple paths are established between the two storage systems, the starting points of the paths
(that is, external ports of the local storage system) and the ending points (that is, WWNs showing
24 Prerequisites