On 05/21/2015 07:56 AM, Chris H wrote:
I am assuming your client's do proper syncs and flushes? What about applications that traditionally write to a BBU backed RAID card and don't explicitly call sync and flushes? I just ask because the only way I can think of handling this is to force sync/flush to a log device of some sort before returning the write was successful. I know this is probably a new use case but this is the best time to address these sort of concerns.
Yeah, that's exactly what we do by default with our existing rbd client side cache. It's writethrough until it sees a flush from the user. For mirroring this wouldn't change, and we could ack writes to the client after only writing them to the rbd journal. This would still be safe since we'd replay any unfinished work in the journal the next time the image was used. Optionally, we could wait for the write to the journal and the regular image data in case the journal is stored in a pool with lower fault tolerance. -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
