IBM DCS3860, Installation, User'S, And Maintenance Manual

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Note: Save a copy of the storage system profile and the Collect All Support
Data bundle when you make configuration changes to the storage system.
Serial port
The serial port on each controller uses a 6-pin Mini-DIN connector. This port is
intended to be used by
service personnel only to provide diagnostic operations on
the RAID controllers. The maximum baud rate is 115200 bps and the factory
default baud rate is 38400 bps.
Attention: Incorrect use of the serial port can result in loss of data access and, in
some cases, in loss of data. Do not make any connections to the serial port unless
you do so under the direct guidance of IBM support personnel.
Cache memory
The data cache memory is a buffer used to temporarily store hard disk drive data
during data read and write operations. Each RAID controller has data cache
memory. The Cache Active LED on the controller turns on when the cache contains
data that is not written to the hard disk drives. The Cache Active LED is off when
there is no data stored in cache. The DCS3860 storage system is available with 24
GB (12 GB per controller) of cache memory.
Cache battery backup module
Each controller contains 12 GB cache memory. The controller also contains a sealed,
rechargeable lithium ion battery that maintains data in the cache so that it can be
transferred to flash memory if the power fails.
Figure 5 shows the locations of the cache battery and memory cache DIMM in the
controller.
The battery chargers in the power supplies perform a battery-learn test when the
storage system is started for the first time and on a regularly scheduled interval
thereafter. Data caching starts after the battery tests are completed.
Memory cache DIMMs (three)
dcsi0074
Figure 5. Cache battery and memory cache DIMM locations
Chapter 1. Introduction
11