nStor 4100FS, Руководство пользователя

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Chapter 2 - Theory of Controller Operation
Stand-Alone Mode
21
Stand-Alone Mode
In Stand-Alone mode, the RAID Controller operates autonomously. The controller
has two Fibre Channel (FC) Host ports, which are labeled in the diagrams as “FC1”
and “FC2.” This operating mode uses both FC host ports.
Advantages:
■
Low cost entry-level RAID storage solution that is field upgradeable.
■
Allows the use of dual host ports to maximize bandwidth and host IOPs.
(For example: this configuration is ideal for sequential access patterns,
where disks can supply more than 160 MB/sec of data to a host.)
■
Host system has multiple paths to each array (with host driver).
■
All arrays appear on both host ports at the same LUN positions in Dual Port
mode. (If both ports are connected to the same host, the host will see a
given array twice unless it does special processing to detect duplicate paths
to array. A host device driver may provide this functionality.)
■
Hosts can detect redundant paths to an array by matching array serial
numbers from SCSI inquiry data.
Disadvantages:
■
The controller is a single point of failure.
■
Third-party software is required for upstream path fail-over.
The following two diagrams depicts the logical function of this operating mode.
Stand-Alone Dual Port with Hubs Disabled
Host I/O Connectors
Drive I/O Connectors
Controller FC Host Ports
RAID Controller
T
SEP
T
T= Location of internal termination
T
T
Controller 1 (A)
SAF-TE Disk I/O
Disk
CH1
Drives 7 - 12
Drives 1 - 6
Disk
CH2
FC2
FC1
P1
P2
CH 1
CH 2
P3
P4
Active
HOST I/O
Active
Controller Disk Ports
SEP
Disk
CH0
Disk
CH3
T
T
T
T
Host SCSI I/O
CH 0
CH 3
4100FS.book Page 21 Tuesday, July 8, 2003 4:35 PM