Hi
I've been idly curious for some time about the notion of supporting write-back in the `md' driver. Safe write-back requires somewhere fast and persistent across power loss/OS reset to put the cache data ... but consumer battery-backed SATA "RAM Drives" offer such a place at an astonishingly reasonable price.
I finally got around to jotting the idea and rationale down here:
http://soapyfrogs.blogspot.com/2010/04/battery-backed-cache-for-linux-software.html
While I'm a mediocre-at-best C coder and am not overly familiar with the kernel, I'm wondering if this is an insane thing for me to try to actually prototype. If you haven't already considered and discarded the notion I'd be interested in your thoughts. Unworkable? Viable but really, really complicated to implement? Or vaguely sensible?
Write caching alone would be wonderful, but it'd also be a stepping stone toward coalescing writes into fewer bigger operations and finally getting rid of any need for hardware RAID controllers...