This is one place where Log-Structured-Merge systems can really prove themselves. There is rarely a need to sync on every change as most of them are independent. You can usually gain lots of write-throughput by syncing at the speed the hardware is optimized for and squeezing as many append-only changes in to those logs. At Orly we've spent quite some time looking at ways to deal with these bottle-necks.
if it is for production, how is your read/write performance?