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LSI SAS RAID
2.3 IM/IME Description
The LSI Logic Integrated Mirroring (IM) feature supports one or two mirrored volumes
on each LSI Logic SAS controller (or one mirrored volume and one Integrated Striping
volume). Typically, one of these volumes is the boot volume, as shown in Figure 2.1.
This is accomplished through the firmware of the LSI Logic SAS controller that
supports the standard Fusion-MPT interface. The runtime mirroring of the boot disk is
transparent to the BIOS, drivers, and operating system.
Host-based status software monitors the state of the mirrored disks and reports any
error conditions. In Figure 2.1 the system is configured with a second disk as a mirror
of the first (primary) disk.
The advantage of Integrated Mirroring (RAID 1), is that there is always a mirrored
copy of the data. The disadvantage is that writes take longer because data must be
written twice. On the other hand, performance is actually improved during reads.
Figure 2.2 shows the logical view and physical view of an Integrated Mirroring
configuration with two disks in the mirrored volume.
B-5
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