Cabling Configuration - nStor Corporation Ultra S2S User Manual

Installation
Cabling Configuration
The cabling configuration section is divided into the following sections: Simplex
Configuration, Duplex (Dual-Active) Configuration, and Duplex (Dual Host)
Configuration. These sections provide a illustrated view of the host computer(s),
CR8e enclosure(s), and cabling schemes when operating in that specific mode.
The Simplex Configuration is the classic configuration supported. In this
configuration a single host is attached to a single CR8e subsystem with an Ultra
S2S RAID Controller to which controls all the drives in the array. Drives are
fault-tolerant when a RAID level providing redundancy is selected and
configured. If the controller or host bus adapter should fail, the data will not be
available until the failure is corrected.
The Duplex (Dual-Active) Configuration supports a single host which is attached
to one or more CR8e subsystems. Each master subsystem has an Ultra S2S RAID
Controller installed and the slave subsystem(s) are connect through daisy-chained
cabling. Under normal active/active mode conditions, both controllers are
actively processing data in parallel. If either controller fails, the other will take
over its functions and continue to process system I/O operations. This is known
as failover.
The Clustering (Dual Host) Configuration supports two host systems connected to
single CR8e subsystem with an Ultra S2S RAID Controller installed. Its advantage
is the ability to sustain data access in the event of the failure of a server or host
adapter. This is also known as failover/failback mode.
When considering the total length of your cabling requirements, you will need to
consider the CR8e internal length of cables and printed circuit board traces
(known as the internal cable length), which must be subtracted from your total
cable length. The CR8e internal cable length is 36 inches.
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Cabling Configuration

For Ultra Wide SCSI (Fast-20), the total cable length is 3 meters (≈9.8 feet)
when four drives are connected to the bus and 3 meters (≈4.9 feet) when
eight drives are connected. After subtracting the CR8e internal length of 36
inches the remaining available cable length is 82 inches or approximately
2.08 meters (≈6.83 feet) when four drives are connected to the bus or
approximately .58 meters (≈1.9 feet) when eight drives are connected.
For Differential Wide SCSI, the total SCSI cable length is 25 meters (≈82 feet).
The internal SCSI bus of the CR8e is a Single-ended bus and therefore a
conversion is required when interfacing to an external differential SCSI host
adapter. The external cable length can be up to a maximum of 25 meters as
described by the SCSI-2 ANSI specifications.