Multipathing The firmware provides support for detecting and using multiple paths from the RAID controllers to the SAS devices that are in enclosures. Devices connected to enclosures have multiple paths to them. With redundant paths to the same port of a device, if one path fails, another path can be used to communicate between the controller and the device. Using multiple paths with load balancing, instead of a single path, can increase reliability through redundancy. Applications show the enclosures and the drives connected to the enclosures. The firmware dynamically recognizes new enclosures added to a configuration along with their contents (new drives). In addition, the firmware dynamically adds the enclosure and its contents to the management entity currently in use. Multipathing provides the following features: Support for failover, in the event of path failure Auto-discovery of new or restored paths while the system is online, and reversion to system load-balancing policy Measurable bandwidth improvement to the multi-path device Support for changing the load-balancing path while the system is online The firmware determines whether enclosure modules (ESMs) are part of the same enclosure. When a new enclosure module is added (allowing multi-path) or removed (going single path), an Asynchronous Event Notification (AEN) is generated. AENs about drives contain correct information about the enclosure, when the drives are connected by multiple paths. The enclosure module detects partner ESMs and issues events appropriately. In a system with two ESMs, you can replace one of the ESMs without affecting the virtual drive availability. For example, the controller can run heavy I/Os, and when you replace one of the ESMs, I/Os should not stop. The controller uses different paths to balance the load on the entire system. In the MegaRAID Storage Manager utility, when multiple paths are available to a drive, the drive information shows only one enclosure. The utility shows that a redundant path is available to a drive. All drives with a redundant path display this information. The firmware supports online replacement of enclosure modules.
Multipathing
The firmware provides support for detecting and using multiple paths from the RAID controllers to the SAS devices that are in enclosures. Devices connected to enclosures have multiple paths to them. With redundant paths to the same port of a device, if one path fails, another path can be used to communicate between the controller and the device. Using multiple paths with load balancing, instead of a single path, can increase reliability through redundancy.
Applications show the enclosures and the drives connected to the enclosures. The firmware dynamically recognizes new enclosures added to a configuration along with their contents (new drives). In addition, the firmware dynamically adds the enclosure and its contents to the management entity currently in use.
Multipathing provides the following features:
Support for failover, in the event of path failure
Auto-discovery of new or restored paths while the system is online, and reversion to system load-balancing policy
Measurable bandwidth improvement to the multi-path device
Support for changing the load-balancing path while the system is online
The firmware determines whether enclosure modules (ESMs) are part of the same enclosure. When a new enclosure module is added (allowing multi-path) or removed (going single path), an Asynchronous Event Notification (AEN) is generated. AENs about drives contain correct information about the enclosure, when the drives are connected by multiple paths. The enclosure module detects partner ESMs and issues events appropriately.
In a system with two ESMs, you can replace one of the ESMs without affecting the virtual drive availability. For example, the controller can run heavy I/Os, and when you replace one of the ESMs, I/Os should not stop. The controller uses different paths to balance the load on the entire system.
In the MegaRAID Storage Manager utility, when multiple paths are available to a drive, the drive information shows only one enclosure. The utility shows that a redundant path is available to a drive. All drives with a redundant path display this information. The firmware supports online replacement of enclosure modules.