Intermix Configurations; Raid-1 & Raid-5 Intermix; Hard Disk Drive Intermix; Figure 2.7 Sample Hard Disk Drive Intermix - Hitachi 9900 User And Reference Manual

2.4

Intermix Configurations

2.4.1 RAID-1 & RAID-5 Intermix
RAID technology provides full fault-tolerance capability for the disk drives of the 9900
subsystem. The 9900 supports RAID-1, RAID-5, and intermixed RAID-1 and RAID-5
configurations, including intermixed array groups within an array domain. The cache
management algorithms (see section 3.3.1) enable the 9900 to stage up to one full RAID
stripe of data into cache ahead of the current access to allow subsequent access to be
satisfied from cache at host channel transfer speeds.
2.4.2

Hard Disk Drive Intermix

Figure 2.7 illustrates an intermix of hard disk drive types. All hard disk drives in one array
group must be of the same capacity and type. The 18-GB, 47-GB, 73-GB, and 146-GB HDDs
can be attached to the same ACP pair. The 180-GB HDDs should not be intermixed with other
HDD types behind the same ACP pair. See the notes under Table 2.3 for important
information on 9900 subsystems which contain 180-GB HDDs.
Disk Array
Unit
Figure 2.7 Sample Hard Disk Drive Intermix
Disk Array Disk Array
Unit Unit
RAID group
RAID5: 3D+1P
RAID1: 2D+2D
Hitachi Lightning 9900™ User and Reference Guide
9900 Disk Array
Controller Unit
4th 2nd
ACP ACP
Pair Pair
3rd 1st
ACP ACP
Pair Pair
RAID group of 180-GB HDD
RAID group of 180-GB HDD
RAID group of 47-GB HDD
RAID group of 18-GB HDD
Disk Array Disk Array
Unit Unit
25