User's Manual

MegaRAID SCSI 320-0 Specifications 4-7
Copyright © 2002 by LSI Logic Corporation. All rights reserved.
4.9.2 Cache Memory
MegaRAID SCSI 320-0 supports 32 to 128 Mbytes of ECC SDRAM
DIMM on-board cache memory. MegaRAID supports write-through or
write-back caching, which can be selected for each logical drive. To
improve performance in sequential disk accesses, MegaRAID does not
use read-ahead caching for the current logical drive. The default setting
for the read policy is Normal, meaning no read-ahead caching. You can
disable read-ahead caching.
Warning:
Write caching is not recommended for the physical drives.
When write cache is enabled, loss of data can occur when
power is interrupted.
4.9.3 MegaRAID BIOS
The BIOS resides on a 1 Mbyte × 8 flash ROM for easy upgrade. The
MegaRAID BIOS supports INT 13h calls to boot DOS without special
software or device drivers. The MegaRAID BIOS provides an extensive
setup utility that can be accessed by pressing <Ctrl><M> at BIOS
initialization. The MegaRAID BIOS Configuration Utility is described in
the MegaRAID Configuration Software Guide.
4.9.4 SCSI Firmware
The MegaRAID SCSI 320-0 firmware handles all RAID and SCSI
command processing and also supports the items in Ta ble 4.7 .
Table 4.7 SCSI Firmware
Feature Description
Disconnect/
reconnect
Optimizes SCSI bus seek.
Stripe size Variable for all logical drives: 2, 4, 8, 16, 32, 64, or 128
Kbytes.
Rebuild Multiple rebuilds and consistency checks with user-
definable priority.