Hardware User's Guide

Intel® RAID Controller RS2VB080/RS2VB040 Hardware User’s Guide 5
— Non-Read Ahead: Always reads from the drive after determining exact location
of each read.
— Adaptive Read Ahead: Reads ahead and caches data only if doing sequential
reads.
— I/O setting: Determines whether read operations check the cache before reading
from disks.
✧ Cache I/O: Checks cache first; only reads disk if data is not in the cache.
✧ Direct I/O: Reads data directly from disk (not cache).
• Redundancy through:
— Configuration stored in non-volatile RAM and on the drives (COD).
— Hot-swap support.
— Optional battery backup for cache memory.
SAS/SATA Features of the LSISAS2108 Controller
• Provides eight independent phys, each supporting 6Gb/s and 3Gb/s SAS data
transfers per PHY.
• Scalable interface that supports up to 32 physical devices and 64 virtual drives
through expanders.
• Supports SSP to enable communication with other SAS devices.
• Supports SMP to communicate topology management information.
• Supports single PHY or wide ports consisting of 2, 3, or 4 PHYs within a single
quad port.
• Allows addressing of multiple SATA targets through an expander if using SATA 2.0-
compliant hard disk drives.
• Allows multiple initiators to address a single target (in a fail-over configuration)
through an expander.
Note: All expander features will not be available at launch.
Online Capacity Expansion and RAID Level Migration Rules
• Migration must occur to the same or larger capacity configuration.
• Migration cannot occur if there is more than one virtual disk in an array.
• Migration and OCE cannot be done on Spanned Arrays (RAID 10, 50, 60).
• Migrations supported are RAID 1 to RAID 0, RAID 5 to RAID 0, RAID 6 to RAID
5, and RAID 6 to RAID 0.
• With OCE, migrations supported are RAID 0 to RAID 1, RAID 0 to RAID 5, RAID
5 to RAID 6, RAID 1 to RAID 6, and RAID 1 to RAID 5.