Dell PERC 4/DC - Manual (Page 49)

Cache Memory
64 MB of cache memory resides in a memory bank for PERC 4/SC and 128 MB for PERC 4/DC. The RAID controller supports write-through or write-back caching,
selectable for each logical drive. To improve performance in sequential disk accesses, the RAID controller uses read-ahead caching by default. You can disable
read-ahead caching.
Onboard Speaker
The RAID controller has a speaker that generates audible warnings when system errors occur. No management software needs to be loaded for the speaker
to work.
Alarm Beep Codes
The purpose of the alarm is to indicate changes which require attention. The following conditions trigger the alarm to sound:
l A logical drive is offline.
l A logical drive is running in degraded mode.
l An automatic rebuild has been completed.
l The temperature is above or below the acceptable range.
l The firmware gets a command to test the speaker from an application.
Each of the conditions has a different beep code, as shown in Table 2 -2 . Every second the beep switches on or off per the pattern in the code. For example, if
the logical drive goes offline, the beep code is three one-second beeps followed by one second of silence.
Table 2-2. Alarm Beep Codes
BIOS
For easy upgrade, the BIOS resides on 1 MB flash memory. It provides an extensive setup utility that you can access by pressing <Ctrl><M> at BIOS
initialization to run the BIOS Configuration Utility.
Background Initialization
Background initialization is the automatic check for media errors on physical drives It makes sure that striped data segments are the same on all physical
drives in an array.
Configuration Features
Alarm Description Code
A logical drive is offline. Three seconds on, one second off
A logical drive is running in degraded mode. One second on, one second off
An automatic rebuild has been completed. One second on, three seconds off
The temperature is above or below the acceptable range. Two seconds on, two seconds off
The firmware gets a command to test the speaker from an application. Four seconds on
NOTE: Unlike initialization of logical drives, background initialization does not clear data from the drives.
The background initialization rate is controlled by the rebuild rate set using the BIOS Configuration Utility, <Ctrl><M>. The default and recommended
rate is 30%. You must stop the background initialization before you change the rebuild rate or the rate change will not affect the background
initialization rate. After you stop background initialization and change the rebuild rate, the rate change takes affect when you restart background
initialization.