It has been awhile since LSI's MegaRAID SAS 9260-8i was available (see SAS RAID Controller Handles Hierarchical Storage) but I have finally got my hands on one (Fig. 1). The eight channel, 6 Gbit/s RAID controller is based on the LSIAS2108 RAID-on-Chip technology. The controller contains 512 Mbytes of DDR2 RAM. EUFI support is standard but battery backup support is optional.
The controller was delivered with LSI's CacheCade Pro 2.0 and FastPath software on-board along support for RAID 5 and 6. These are extra options so it is possible to install what your system requires. For example, if RAID 1 is sufficient but you want SSD caching support then CacheCade is all that is required. FastPath is designed to optimize SSD arrays.
As usual, your mileage may vary and most installations will concentrate on one type of configuration based on the application mix. For example, a high performance transaction system might employ SLC (single-level cell) SSDs that have higher write endurance than MLC (multi-level cell) SSDs and FastPath is probably the best choice. Large hard drive arrays with SSD caching would employ CacheCade.
Because of this variance in architectures I am going to be addressing installation, configuration and features rather than performance. Getting the same results of any tests I would do would require identical hardware. In general, CacheCade provided near SSD performance overall when mixed with a hard drive array and FastPath enabled SSDs were almost twice as fast as the same array without FastPath enabled.
I popped it into SuperMicro's 4U AS-4022G-6F A+ Server (Fig. 2) that had two, 16-core Opteron 6000 Series processors (see Hands-on SuperMicro's 32-core A+ Server). The original testing for that project was done using the built-in LSI SAS controller but for this test I disconnected the on-board controller and used only the SAS 9260-8i.
The 2.5-in drives used with the tests included five Seagate SAS enterprise 15K Savvio drives (see Family Of Drives Span Enterprise Storage Needs) plus SSD drives from Micron. These includeded RealSSD P300 (see Building A Hybrid RAID NAS Server) and the Micron RealSSD P400e SSD drives. The P300 is an SLC enterprise drive while the P400e is an MLC enterprise drive. All the drives run at 6 Gbits/s. The SSDs had SATA II interfaces.
The P400e's read performance is 50,000 IOPs random and 350 Mbytes/s sequential. The P300's read performance is a little better at 60,000 IOPs random and 360 Mbytes/s sequential but its sustained random write IOPs exceeds 16,000.
I swapped the P300 and P400e drives when running performance tests. They were on par for read support and caching and the P300 performed better for writes as expected. The choice is not necessarily cut and dried since users will need to consider cost and drive life based on their application requirements.