Specifications
Escala Tower PL & S, E, T System Hardware
Chapter 3: External Storage and SAN Subsystems 17/116
9es3s1c3.doc
Rev 5.9
02/12/2003
2.1.4.4. Architecture: SP, LCC, disks, memory
2.1.4.4.1. SPs (Storage Processors) and host interface
The SP provides the following features to the disk subsystem:
•
RAID processing
•
host interface management
•
backend management
•
memory
•
built-in hub for external connection
•
Fibre Channel circuitry for backend.
Each SP has 3 fibre channel connectors.
Port A and port B connectors correspond to a built-in hub, offering a 100 MB/s logical connection.
Using these connectors, 2 devices (like HBA within servers) can be connected to the same SP, without
any external device. They share the 100 MB/s bandwidth. Above two devices, an external hub must be
used.
The host interface implements the FCP-SCSI-3 protocol. Command tag queuing is implemented.
The third connector is a DB9 expansion connector (EXP) which enables the connection to an
additional DAE enclosure. It is not possible to chain more than 2 DAEs. When iDAE is equipped with
two SPs, two distinct internal fibre channel loops are available, and the chained DAEs must be
equipped with dual LCCs. In the event of a failure, disk access remains possible through the other SP.
The distance between iDAE and DAE or between chained DAE enclosures is limited to 10m with
copper cables.
2.1.4.4.2. Power Supplies (and PDUs)
iDAE enclosures can be equipped with one or two power supplies. Each power supply supports a fully
configured enclosure and shares power with the other power supply if present. Each power supply is
equipped with its own power cord, making the connection to two different power sources possible.
2.1.4.4.3. Standby Power Supply (SPS)
The SPS protects the iDAE against external power supply failures, and enables to properly stop a disk
subsystem in case of power outage.
SPS are optional, but at least one SPS must be installed to use the write cache. Optionally, a second
SPS can be installed to provide higher availability.
The SPS is also named BBU (Battery Backup Units).