Raid Systems For The Tape Volume Cache - Fujitsu Siemens Computers pmn User Manual

Hardware architecture

2.2.2 RAID systems for the Tape Volume Cache

A TVC (Tape Volume Cache) is the heart of the entire virtual archive system. It represents
all of the Tape File Systems in which the logical volumes can be stored temporarily. One or
more RAID systems (up to 8) are used for this.
Each RAID system contains at least the basic configuration, which consists of FC disks and
2 RAID controllers. It can also be equipped with up to 7 extensions, which in turn constitute
a fully equipped shelf with FC or ATA disks. A RAID system consists of shelves which in
CentricStor are always fully equipped with disks. The TVC illustrated in the figure below
contains 2 RAID systems with a total of 12 equipped shelves:
TVC
1st RAID system
basic config.
Contr. 0
Figure 7: 2 RAID systems form the TVC
In the case of the FibreCat CX3-20, for example, the 300-GB FC disks used offer a net ca-
pacity of 900 GB per RAID group. Here the basic configuration and each extension contain
3 RAID groups, resulting in a net capacity of 3 * 0.9 TB = 2.7 TB for each shelf. The net
capacity of the maximum configuration of a RAID system is therefore 8 * 2.7 TB = 21.6 TB.
One RAID group is used for one cache file system, which means that the basic configuration
and each extension contain 3 cache file systems and one RAID system with the maximum
configuration with 24 cache file sytems.
30
extension
extension
extension
extension
extension
extension
extension
Contr. 1
2nd RAID system
basic config.
extension
extension
extension
Contr. 0 Contr. 1
CentricStor - Virtual Tape Library
U41117-J-Z125-7-76