On Mon, 14 Feb 2011 22:38:17 +0100 Andras Korn <korn@xxxxxxxxxxxxxxxxxxxxxxx> wrote: > Hi, > > I experimented a bit with write-mostly and write-behind and found that > write-mostly provides a very significant benefit (see below) but > write-behind seems to have no effect whatsoever. The use-case where write-behind can be expected to have an effect is when the throughput is low enough to be well within the capacity of all devices, but the latency of the write-behind device is higher than desired. write-behind will allow that high latency to be hidden (as long as the throughput limit is not exceeded). I suspect your tests did not test for low latency in a low-throughput scenario. NeilBrown -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
