>Isn't this done via pipelining anyway? Yes, it's the way it's done. >So there's no notion of ordering with respect 1st, 2nd, and 3rd block, either >all writes go through the pipeline or none are. Still correct.
> When the write request returns to the client there will be a local copy, a > copy on another machine in the same, and a copy on a machine in a different > rack, who cares about the ordering inside the pipeline? Not necessary. There might not be any additional copy on a different machine on the same rack. BUT.. As you said, who cares ;) As long as we have the local copy and some replicas. I have updated the documentation already. I will open the JIRA and submit. I have also added subsequent replicas in case replication factor is > 3. JM 2013/4/4 lars hofhansl <[email protected]>: > Isn't this done via pipelining anyway? > So there's no notion of ordering with respect 1st, 2nd, and 3rd block, either > all writes go through the pipeline or none are. > > When the write request returns to the client there will be a local copy, a > copy on another machine in the same, and a copy on a machine in a different > rack, who cares about the ordering inside the pipeline? > > > Seems it would also be inefficient to pipeline from the local rack to another > another one and then in the same pipeline back into the local rack (more load > on the switch connecting the racks with no benefit). > > I'll double check. > > > -- Lars > > > > ________________________________ > From: Jean-Marc Spaggiari <[email protected]> > To: [email protected] > Sent: Thursday, April 4, 2013 8:25 AM > Subject: Re: confused info about region-regionserver locality > > Hi, > > I think you're right and documentation need to be updated. > > The 3rd replica is written on a random node in the same rack as the > 2nd replica. I will double check. Can you please open a JIRA so this > is updated? > > JM > > 2013/4/4 KIM JUN YOUNG <[email protected]>: >> Hi All. >> >> There is confused understanding about region-regionser locality. >> >> from the current document , >> >> http://hbase.apache.org/book/regions.arch.html >> 9.7.3. Region-RegionServer Locality >> Over time, Region-RegionServer locality is achieved via HDFS block >> replication. The HDFS client does the following by default when choosing >> locations to write replicas: >> >> First replica is written to local node >> Second replica is written to another node in same rack >> Third replica is written to a node in another rack (if sufficient nodes) >> >> >> but, my understanding is different >> HDFS write blocks for replica >> >> first, local node >> second, another node in another rack >> third, random another node in same rack >> >> need to be changed? or am I missing something?
