On Wednesday July 13, jdc@xxxxxx wrote: > Question for the list: if I'm doing a long sequential write, naively > each parity block will get recalculated and rewritten several times, > once for each non-parity block in the stripe. Does the write-caching > that the kernel does mean that each parity block will only get written > once? Raid5 does the best it can. It delays write requests as long as possible, and then when it must do the write, it writes every other block in the stripe that it has been asked to write, so only one parity update is needed for all those blocks. My tests suggest that for long sequential writes (Without syncs) this achieves full-stripe writes most of the time. 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
