Specifications

Escala Tower PL & S, E, T System Hardware
Chapter 3: External Storage and SAN Subsystems 24/116
9es3s1c3.doc
Rev 5.9
02/12/2003
Each SP has 2 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 devices. They share the 100 MB/s of
bandwidth. Above two devices, an external hub or switch must be used.
The host interface implements the FCP-SCSI-3 protocol. Command tag queuing is implemented, with
up to 256 tags.
2.1.5.4.2. LCC (Link Control Cards)
DPE enclosures can be equipped with one or two LCCs (depending on the number of SP). The LCC
receives and electrically terminates the incoming FC-AL signal from the host or other kind up “up
stream” devices. The LCC passes the input signal to its disk drives and then conducts the output
signal, via cables, to an LCC of the next DAE in the loop (if any). In addition, each LCC monitors the
environmental status of the enclosure.
There is a one-to-one relation between SPs and LCCs. Either the DPE enclosure has one SP and one
LCC, or the DPE has 2 SPs and 2 LCCs. When enclosures are equipped with two LCCs, two distinct
internal fibre channel loops can be implemented, and all the DAE enclosures chained in the backend
must have 2 LCCs each. In the event of a failure, disk access remains possible through the other
SP/LCC.
The connector of the LCC of the DPE enclosure is reserved for the connection to another DAE.
Technically, up to 9 DAE enclosures can be chained to create a RAID subsystem with 100 disk
capacity (10 in PDE plus 9x10 in DAE enclosures). Interconnection is made with copper cables.
The distance between DPE and DAE or between chained DAE enclosures is limited to 10m with
copper cables.
2.1.5.4.3. Power Supplies (and PDUs)
DPE 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 supply is
equipped with its own power cord, making the connection to two different power sources possible.
2.1.5.4.4. Standby Power Supply (SPS)
The SPS protects the DPE against external power supply failures, an enable 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 referred to as BBU (Battery Backup Units).