Posted May 16, 2012 18:14 UTC (Wed) by butlerm (subscriber, #13312)
Parent article: A bcache update
Next question. Considering that there is a write back cache on persistent media, does that mean when the block layer issues a write cache flush (force unit access) command, that bcache synchronously forces the blocks to SSD, but _not_ synchronously to the backing store device?
Assuming the cache is reliable and persistent, that is exactly what you want in most situations. If a higher level cache flush command actually forces a cache flush of a persistent write back cache, write back mode will be approximately useless. You might as well just leave it in RAM.