Accusys ExaRAID GUI - Manual (Page 279)

Appendix
B-10
• Seasoned redundancy design
The storage system availability is achieved by the redundancy design to
eliminate single point of failure. The controller is equipped with redundant
flash chips with advanced algorithms for error checking and bad block
reallocation in the firmware to protect the controller from defect flash
blocks and ensure longer life time of the controller. The firmware stores two
copies of RAID meta data as well as bad block reallocation map on disk
drives to avoid any data or RAID loss resulted from bad sectors.
• Support multi-path
Supporting multi-path solutions at host side, such as Microsoft® MPIO, system
continuity can be achieved because the storage system can tolerate
failures on the IO path, such as host bus adapters, switches, or cables, by
distributing IO over multiple IO paths. This also improves performance by the
dynamic load balancing as well as simplifies the storage presentation
process.
• Support active-active redundant controller
The controller supports dual active-active configuration to tolerate
controller failure. The host IO access and background tasks of a failed
controller can be online taken over by the survival controller. And when the
failed controller is replaced by a new controller, the system will return to
optimal operation by redistributing the host IO access and background
tasks back to the original controller.
• Support UPS monitoring
The firmware can monitor the attached UPS by the SMART UPS protocol
through the RS232 ports. When the AC power is gone, the firmware will
conduct the graceful shutdown to avoid unwanted data loss. The
administrator can also configure the UPS to determine the shutdown and
restart policies.
• Online array roaming
When a storage system cannot be recovered in a short time, the best
choice to put the data on disk drives back online is to conduct the array
roaming, by which the disk drives can be installed in another storage
system, and the RAID configurations are recovered instantly. Besides, the
background tasks previously running on the disk drives are also resumed.
With the online array roaming, the administrator can online install the disk
drives one by one to the system, and import the disk groups later. This avoids
disrupting the running storage system, and simplifies the roaming process.
• Online array recovery
There are chances of RAID crash resulted from the transient failure of
multiple disk drives, and the disk drives can still be working after being re-
powered. The drives might stall when its firmware is locked or be unstable as
they are getting old. It could also be because of the abnormal