Asus LSI SAS3442X-R - Manual (Page 20)

2-4 Overview of Integrated Mirroring and Integrated Mirroring Enhanced
Version 1.1 Copyright © 2006, 2007 by LSI Logic Corporation. All rights reserved.
Figure 2.1 Typical Integrated Mirroring Implementation
The advantage of an IM/IME volume is that there is always a second,
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 IM volume.
Figure 2.2 Integrated Mirroring Volume
An IME volume can be configured with up to ten mirrored disks. (One or
two global hot spares can be added also.)
Figure 2.3 shows the logical
view and physical view of an Integrated Mirroring Enhanced (IME)
volume with three mirrored disks. Each mirrored stripe is written to a disk
and mirrored to an adjacent disk. This type of configuration is also called
RAID 1E.
IM Volume
Primary Mirror
NVSRAM
FLASH
(For Configuration)
(For Write Journaling)
LSI
Memory
Bus
SAS
Fusion-MPT
Controller
LBA 1
LBA 2
LBA 3
LBA N
+
Logical View Physical View
LBA 1’
LBA 2’
LBA 3’
LBA N’
LBA 1
LBA 2
LBA 3
LBA N