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DuraStor 412R/6320SS/7320SS Installation and User’s Guide
survivor asserts. This is accomplished using Storage Manager Pro
or the Disk Array Administrator.
If you replace a failed controller with a new controller, the new
controller will attempt to retrieve its configuration (see
Understanding Mirrored Operations
) from the
surviving controller. This means that the replacement controller
will boot up with the same configuration as the controller it
replaced.
If the surviving controller for some reason does not contain a valid
mirrored configuration, then the user must manually configure the
replacement controller. The correct host target ID must be set, and
the active-active operating mode must be enabled.
The active-active controller system makes some assumptions about
the host operating system’s SCSI processing. Specifically, the host
must retry incomplete commands after a specific time period. This
retry is necessary because a host may issue a command to a
controller, the controller fails over, and the new controller does not
have a copy of the command.
Advantages:
■
LUN isolation with the single-port, single host system.
■
Access to all LUNs with the quad cabling configuration.
■
Provides transparent fail-over and fail-back.
Disadvantages:
■
Host HBA or the Host SCSI bus are single points of failure.
■
In a single host configuration, the host system is also a single
point of failure.
■
No upstream fail-over with a single host dual HBA
configuration. Upstream fail-over requires dual host with quad
cabling and third-party file share/file lock software.
■
Protected LUN sharing between two host systems is not
supported without the use of third-party file share/file lock
software.
DuraStor IUG - Online.book Page 10 Friday, July 19, 2002 3:06 PM
