Hitachi 9960 Capacities and RAID Architecture, Storage Capacity of the Lightning 9900 Series

Capacities and RAID

Architecture

Storage Capacity of the Lightning 9900™ Series

The Lightning 9900™ Series supports an unmatched range of capacities as shown in Table 3.

System Capacities and Number of disk drives for various configurations

Raw System	Raw capacity with	Raw capacity with	Raw capacity with
Configuration	18GB drives	73GB drives	180GB drives
Lightning 9960
One Array Frame	1.7TBs = 96 disks	7.0TB = 96 disks	16.6TB = 96 disks
Lightning 9960
Six Array Frames	9.4TB = 512 disks	37.4TB = 512 disks	88.3TB = 512 disks
Lightning 9910	.9TB = 48 disks	3.5TB = 48 disks	8.3TB = 48 disks

Advantages of the Lightning 9900™ Series RAID Hardware

Hitachi designs the most advanced RAID (Redundant Array of Independent Disks) controllers in enterprise storage to interface to its disk subsystems. These intelligent controllers provide disk interface and RAID management, offloading these tasks to dedicated processors. Each Lightning 9900™ Series ACP controller supports RAID-1+ and RAID-5 (parity RAID). All disks in the system are defined as part of a RAID array of one type or another. Non-volatile RAM on each controller accelerates RAID functions, particularly disk writes.

RAID-1+

With the announcement of the Lightning 9900 Series RAID-1+ was introduced. RAID-1+ is a 2 Data + 2 Data disk arrangement (four disks total) in a RAID-1+0 configuration with a twist – a rotating copy.

RAID-5 – Distributed Parity

RAID-5 arrays consist of four disks. Data is striped across RAID-5 arrays in a fashion similar to RAID-1+, but RAID-5 provides fault resilience by keeping parity information on each stripe of data. If a failure occurs, the contents of that block can be recreated by reading back the other blocks in the stripe along with the parity. Parity information is distributed throughout the array to minimize potential bottlenecks in the event of a need to rebuild data from a failed disk. The overhead of RAID-5 is equivalent to one disk drive, regardless of the size of the array.

RAID Rebuild Capability

In the event of a disk failure, RAID-1+ or RAID-5 arrays can be rapidly and automatically rebuilt using available “hot-spare” drives. The Lightning 9900™ also allows logical volumes to be expanded online. Configurations for RAID-1+ and RAID-5 are shown in Figure 20.

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Table 3 – System capacities and number of disk drives for various configurations.

Intelligent controllers offload tasks to dedicated processors.

RAID-1+ is unique to Hitachi.

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