System and method for a reserved memory area shared by all redundant storage controllers
View Patent ↗A fibre channel storage area network (SAN) provides virtualized storage space for a number of servers to a number of virtual disks implemented on various virtual redundant array of inexpensive disks (RAID) devices striped across a plurality of physical disk drives. The SAN includes plural controllers and communication paths to allow for fail-safe and fail-over operation. The plural controllers can be loosely-coupled to provide n-way redundancy and have more than one independent channel for communicating with one another. In the event of a failure involving a controller or controller interface, the virtual disks that are accessed via the affected interfaces are re-mapped to another interface in order to continue to provide high data availability. In particular, a common memory storage device is connected to the back-ends of every controller to provide a storage area. In this manner, the common memory storage device can be accessed via operations similar to those a controller already uses to presently access the physical disks which are connected to the back-end of the controllers.
1. A storage area network comprising:
a plurality of loosely-coupled storage controllers arranged in a redundant configuration to provide, to a plurality of servers, access to virtualized storage, wherein one of the storage controllers operates as a master storage controller and the other storage controller or controllers operate as slave storage controllers; and
means, accessible by all storage controllers, for storing information relating to a configuration of the storage area network;
wherein the storage area network comprises a plurality of physical disk drives coupled to a respective back-end of each of the storage controllers, said physical disk drives being configured to provide the virtualized storage; and
the means for storing comprises a respective portion on each one of the physical disk drives, wherein the information relating to the configuration is stored in each of the respective portions.
2. The storage area network according to claim 1 , wherein each respective portion is write accessible to only the master controller but read accessible by all the storage controllers.
3. The storage area network according to claim 1 , wherein the information relating to the configuration includes at least one of network interface configuration information for each slave controller, an identifier associated with the master controller, a system identifier associated with all of the storage controllers, a respective identifier for each of the storage controllers; statistical information relating to operation of each of the storage controllers, a log of events occurring on each of the storage controllers, and results of an election process performed by the storage controllers to elect a master controller.
4. The storage area network according to claim 1 , wherein:
each storage controller further comprises a respective software routine, that when executing on the storage controller, is configured to retrieve selected data from the information related to the configuration.
5. The storage area network according to claim 4 , wherein each software routine is further configured to attempt to retrieve the selected data from any of the respective portions until the selected data is successfully retrieved.
6. A method, in a storage area network comprising plural loosely-coupled redundant controllers, for providing a common information area, the method comprising the steps of:
arranging the controllers to include a master controller and one or more slave controllers;
allocating a respective storage portion on each of a plurality of physical disk drives which are coupled to a respective back-end of each controller;
storing in each respective storage portion a respective copy of information relating to a configuration of the controllers; and
permitting each controller to have read access to all of the respective storage portions.
7. The method according to claim 6 , further comprising the steps of:
preventing the one or more slave controllers from having write access to all of the respective storage portions.
8. The method according to claim 6 , wherein the information relating to the configuration includes at least one of network interface configuration information for each slave controller, an identifier associated with the master controller, a system identifier associated with all of the controllers, a respective identifier for each of the controllers; statistical information relating to the operation of each of the controllers, a log of any events occurring on each of the controllers, and results of any election process performed by the controllers to elect a master controller.
9. The method according to claim 6 , further comprising the steps of:
reading the respective storage portion, by each controller upon powering up, in order to retrieve respective configuration information associated with a particular controller; and
implementing the respective configuration information during operation of the associated controller.