By Dave Simpson
-- The 3.5 release of LSI's MegaRAID software/firmware, which works with the company's MegaRAID SAS 8700 and 8800 family of 3Gbps SAS/SATA adapters (aka controllers), includes a number of enhancements – most notably, multipathing and load balancing.
The single-controller multipathing feature (as opposed to dual-controller failover with cache coherency) enables a controller to fail over to an alternate path in the event of a failure in a primary cable or port on a dual-port drive for increased reliability and fault tolerance.
The load balancing feature can increase performance by as much as 40% in the case of large-block sequential reads, according to Tom Kodet, LSI's worldwide channel marketing manager. Load balancing distributes read/write I/Os over multiple paths (two paths in the case of the MegaRAID SAS 8700 and 8800 adapters). Kodet notes that load balancing can be particularly advantageous in applications such as virtual tape libraries (VTLs), video streaming, and data backup and archiving.
Other new features in the 3.5 release of MegaRAID firmware include:
--Revertible hot spare, which allows users to automatically restore a hot spare and logical drive to their original configuration after a failed drive is replaced. The key benefit is reduced maintenance.
--RAID-1 extensions that allow users to support larger logical volumes and to configure RAID-1 arrays with up to 32 drives per volume (as opposed to the traditional limit of two drives). Users can also extend RAID-10 configurations from the typical limit of 16 drives up to the maximum number of drives supported by the adapter. Kodet notes that large RAID-10 volumes are particularly advantageous in applications such as Microsoft Exchange. The RAID-1 extensions are based on definitions from the Storage Networking Industry Association (SNIA).
Lastly, MegaRAID 3.5 now supports Microsoft's Virtual Disk Service.
LSI's 8704EM2 adapter is priced at $399, while the 8880EM2 is priced at $799.