Hitachi Universal Storage Platform VM - Manual (Page 35)

Architecture and Components 2-9
Hitachi Universal Storage Platform V/VM User and Reference Guide
Back-End Directors and Array Domains
The back-end director (BED) features control the transfer of data between the
data drives and cache. The BEDs are installed in pairs for redundancy and
performance. The USP V can be configured with up to eight BED pairs,
providing up to 64 concurrent data transfers to and from the data drives. The
USP VM is configured with one BED pair, which provides eight concurrent data
transfers to and from the data drives. The USP V/VM supports two types of
BED features, standard and encrypting. The encrypting BED (EBED) provides
data encryption for both open and mainframe systems.
The data drives are connected to the BED pairs by fibre cables using an
arbitrated-loop (FC-AL) topology. Each BED pair has eight independent fibre
back-end paths controlled by eight back-end microprocessors. Each dual-
ported fibre-channel drive is connected through its two ports to each board in
a BED pair over separate physical paths (loop switch in between the drives and
ports) for improved performance as well as redundancy.
Table 2-2 lists the BED specifications. Each BED pair contains eight buffers
(one per fibre path) that support data transfer to and from cache. Each dual-
ported drive can transfer data over either port. Each of the two paths shared
by the drive is connected to a separate board in the BED pair to provide
alternate path capability. Each BED pair is capable of eight simultaneous data
transfers to or from the data drives.
Table 2-2 BED Specifications
Parameter Specifications
Number of back-end director features USP V: 1 – 8
USP VM: 1
Types of back-end director features Standard
Encrypting
Back-end paths per BED feature 8
Back-end paths per storage system USP V: 8 – 64
USP VM: 8
Back-end array interface type Fibre-channel arbitrated loop (FC-AL)
Back-end interface transfer rate (burst rate) 400 MB/sec (4 Gbps)
Maximum concurrent back-end operations per BED feature 8
Maximum concurrent back-end operations per storage system USP V: 64
USP VM: 8
Back-end (data) bandwidth USP V: 68 GB/sec
USP VM: 8.5 GB/sec