On Friday May 25, Stefan.Bader@xxxxxxxxxx wrote: > 2007/5/25, Neil Brown <neilb@xxxxxxx>: > > - Are there other bit that we could handle better? > > BIO_RW_FAILFAST? BIO_RW_SYNC? What exactly do they mean? > > > BIO_RW_FAILFAST: means low-level driver shouldn't do much (or no) > error recovery. Mainly used by mutlipath targets to avoid long SCSI > recovery. This should just be propagated when passing requests on. Is it "much" or "no"? Would it be reasonable to use this for reads from a non-degraded raid1? What about writes? What I would really like is some clarification on what sort of errors get retried, how often, and how much timeout there is.. And does the 'error' code returned in ->bi_end_io allow us to differentiate media errors from other errors yet? > > BIO_RW_SYNC: means this is a bio of a synchronous request. I don't > know whether there are more uses to it but this at least causes queues > to be flushed immediately instead of waiting for more requests for a > short time. Should also just be passed on. Otherwise performance gets > poor since something above will rather wait for the current > request/bio to complete instead of sending more. Yes, this one is pretty straight forward.. I mentioned it more as a reminder to my self that I really should support it in raid5 :-( NeilBrown -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
