> There is some hardware solution, e.g. Intel made the http://ark.intel.com/products/70029/Intel-RAID-SSD-Cache-Controller-RCS25ZB04 0LX using the "Nytro MegaRAID" chip. > > Someone would need to port its driver to OpenBSD. > > Also in the past there was a "Adaptec MaxIQ". Those are the only two "Raid controller cache" hardware solutions I am aware of, do you know any more? > > >
Some of the MegaRaid cards feature cache cade. Essentially disk cache is written to SSD before being “copied” to spinning disk. Keep in mind DRAM based cache can improve performance when implemented in conjunction with hardware write back. Also magnetic disk & SSD with super cap / fault tolerant on disk cache can seed up I/O significantly..