HP XP Array Manager Software - Manual (Page 18)

2-4 About Cache Manager Operations
Hitachi Cache Manager User’s Guide
Overview of Priority Mode and Bind Mode
Priority Mode
In Priority Mode (normal mode), the total capacity of cache required is:
Standard cache + cache required for Cache Manager + Additional cache
The main advantage of priority mode is that read data is transferred at host
data transfer speed. In priority mode the cache extents are used to hold read
data for specific extents on volumes. Write data is write duplexed in normal
cache and de-staged to disk using standard algorithms. Because there is no
duplexed write data in the cache reserved for Cache Manager, all priority mode
cache extents are 100% utilized by user read-type data.
For mainframe volumes, one slot is 66 kB. This requires 4 cache segments
(16.5 kB/segment). Sixteen (16) slot images for mainframe require 1,056 kB
of reserved cache.
Note: Even though a track for 3390 volumes is 56 kB, because cache is
divided into 16.5 kB segments, it will require four segments. A 3380 slot
(track) is 48 kB, so three 16 kB segments will be sufficient.