HP Tool Storage 354903-001 User Manual download pdf (Page 40)

40 HP MSA 500 G2 Storage System Maintenance and Service Guide

NOTE: The data protection and the time limit also apply if a power

outage occurs. When power is restored to the system, an initialization

process writes the preserved data to the hard drives.

To enable faster data access from disk storage, the battery module performs two

types of caching:

• Posted-write caching—the controller writes user data in the cache memory

on the module rather than directly to the drives. Later, when the storage

system is idle, the controller writes the data to the drive array.

• Read-ahead caching—the controller detects sequential array access, reads

ahead into the next sequence of data, and stores the data in the read-ahead

cache. Then, if the next read access is for the cached data, the controller

immediately loads the data into system memory, avoiding the latency of a

disk access.

SCSI IDs

Bay SCSI ID Bus Port

1 0 0

2 1 0

3 2 0

4 3 0

1 2 ... 35 36 37 38 39 40 41 42 43 44 45 ... 51 52

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HP Tool Storage 354903-001 User Manual Page 40