HP StorageWorks Secure Path V3.0C for Linux and Linux Workgroup Edition Installation and Reference Guide (AA-RU7VD-TE, February 2004)

Secure Path Technology
22 Secure Path v3.0C for Linux and Linux Workgroup Edition Installation and Reference Guide
Controller ownership
Storage systems that are multiple-bus capable generally contain a pair of
redundant controllers and support one of the following basic operational models:
■ The MSA1000 uses the active/passive operational model. In the
active/passive model, all storagesets are assigned ownership to one controller
of the pair for I/O processing. The other controller is standby and is available
as a substitute in case of failure on the original.
■ The HSG80, EVA5000, and EVA3000 use the modified active/active
operational model. In the active/active model, I/O processing may be routed
through both controllers simultaneously, providing better performance in
addition to high availability. The RAID arrays supported by Secure Path
implement a modified version of the active/active model. Although I/O can be
processed simultaneously by both controllers, any given storageset is owned
or online to a host through only one controller.
Ownership of a storageset may be transferred to the other controller at any
time through a host-initiated command sequence. However, because the
ownership transfer results in controller cache flushing and I/O wind down, the
storageset may become inaccessible for a period of several seconds. Arbitrary
ownership transfers are never automatically initiated by Secure Path and
should be avoided.
Note: Secure Path automatically retries I/O requests that terminated in error due to
ownership transfers. It also queues new I/O requests until the ownership transfer has
completed, to ensure data integrity.