+gluster-devel ----- Original Message ----- > From: "Milind Changire" <mchangir@xxxxxxxxxx> > To: "Raghavendra Gowdappa" <rgowdapp@xxxxxxxxxx> > Cc: "rhs-zteam" <rhs-zteam@xxxxxxxxxx> > Sent: Thursday, February 9, 2017 11:00:18 PM > Subject: patch for "limited performance for disperse volumes" > > My first comment was: > looks like patch for "limited performance for disperse volume" [1] is going > to be helpful for all other types of volumes as well; but how do we > guarantee ordering for writes over the same fd for the same offset and > length in the file ? > > then thinking over a bit and in case you missed my comment over IRC: > I was thinking about network multi-pathing and rpc requests(two writes) > being routed through different interfaces to gluster nodes which might > lead to a non-increasing transaction ID sequence and hence might lead > to incorrect final value if the older write is committed to the same > offset+length > > then it dawned on me that for blocking operations the write() call > wont return until the data is safe on the disk across the network or > the intermediate translators have cached it appropriately to be > written behind. > > so would the patch work for two non-blocking writes originating for the > same fd from the same thread for the same offset+length and being > routed over multi-pathing and write #2 getting routed quicker than > write #1 ? To be honest I've not considered the case of asynchronous writes from application till now. What is the ordering guarantee the OS/filesystems provide for two async writes? For eg., if there are two writes w1 and w2, when is w2 issued? * After cbk of w1 is called or * parallely just after async_write (w1) returns (cbk of w1 is not invoked yet)? What do POSIX or other standards (or expectation from OS) say about ordering in case 2 above? [1] https://review.gluster.org/15036 > > just thinking aloud > > -- > Milind > _______________________________________________ Gluster-devel mailing list Gluster-devel@xxxxxxxxxxx http://lists.gluster.org/mailman/listinfo/gluster-devel
