On Sun, 19 Dec 2010, Tatsuya Kawano wrote: > Is there any example of asynchronous IO on RADOS (librados)? When I > write some bytes to an object, I'm only interested on the ack, which > means writes are applied to all the OSDs within the same placement group > but not yet committed to the disks. I'll use this feature to write HBase > journals. There is an example in the rados_bencher.h file, and in testrados[pp].c[c]. One thing to keep in mind, though, is that in some cases commit is actually faster. Sometimes writing to the fs can be bursty (latency spikes while btrfs is doing a commit). If you have a writeahead journal, the commit always comes first. And if you have a fast journal device (SSD, NVRAM, RAID card with NVRAM, etc.) it will also be predictably fast. And if it's a journal you rely on for consistency, I'd be very careful about relaxing your safety guarantees! sage -- 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
