On Mar 24, 2013, at 4:34 PM, Jamal B <[email protected]> wrote: > It shouldn't cause further problems since most of your small nodes are > already their capacity. You could set or increase the dfs reserved property > on your smaller nodes to force the flow of blocks onto the larger nodes. > >
Thanks. Can you please specify which are the dfs properties that we can set or modify to force the flow of blocks directed towards the larger nodes than the smaller nodes ? ----- > > On Mar 24, 2013 4:45 PM, "Tapas Sarangi" <[email protected]> wrote: > Hi, > > Thanks for the idea, I will give this a try and report back. > > My worry is if we decommission a small node (one at a time), will it move the > data to larger nodes or choke another smaller nodes ? In principle it should > distribute the blocks, the point is it is not distributing the way we expect > it to, so do you think this may cause further problems ? > > --------- > > On Mar 24, 2013, at 3:37 PM, Jamal B <[email protected]> wrote: > >> Then I think the only way around this would be to decommission 1 at a time, >> the smaller nodes, and ensure that the blocks are moved to the larger nodes. >> >> And once complete, bring back in the smaller nodes, but maybe only after you >> tweak the rack topology to match your disk layout more than network layout >> to compensate for the unbalanced nodes. >> >> Just my 2 cents >> >> >> On Sun, Mar 24, 2013 at 4:31 PM, Tapas Sarangi <[email protected]> >> wrote: >> Thanks. We have a 1-1 configuration of drives and folder in all the >> datanodes. >> >> -Tapas >> >> On Mar 24, 2013, at 3:29 PM, Jamal B <[email protected]> wrote: >> >>> On both types of nodes, what is your dfs.data.dir set to? Does it specify >>> multiple folders on the same set's of drives or is it 1-1 between folder >>> and drive? If it's set to multiple folders on the same drives, it is >>> probably multiplying the amount of "available capacity" incorrectly in that >>> it assumes a 1-1 relationship between folder and total capacity of the >>> drive. >>> >>> >>> On Sun, Mar 24, 2013 at 3:01 PM, Tapas Sarangi <[email protected]> >>> wrote: >>> Yes, thanks for pointing, but I already know that it is completing the >>> balancing when exiting otherwise it shouldn't exit. >>> Your answer doesn't solve the problem I mentioned earlier in my message. >>> 'hdfs' is stalling and hadoop is not writing unless space is cleared up >>> from the cluster even though "df" shows the cluster has about 500 TB of >>> free space. >>> >>> ------- >>> >>> >>> On Mar 24, 2013, at 1:54 PM, Balaji Narayanan (பாலாஜி நாராயணன்) >>> <[email protected]> wrote: >>> >>>> -setBalancerBandwidth <bandwidth in bytes per second> >>>> >>>> So the value is bytes per second. If it is running and exiting,it means it >>>> has completed the balancing. >>>> >>>> >>>> On 24 March 2013 11:32, Tapas Sarangi <[email protected]> wrote: >>>> Yes, we are running balancer, though a balancer process runs for almost a >>>> day or more before exiting and starting over. >>>> Current dfs.balance.bandwidthPerSec value is set to 2x10^9. I assume >>>> that's bytes so about 2 GigaByte/sec. Shouldn't that be reasonable ? If it >>>> is in Bits then we have a problem. >>>> What's the unit for "dfs.balance.bandwidthPerSec" ? >>>> >>>> ----- >>>> >>>> On Mar 24, 2013, at 1:23 PM, Balaji Narayanan (பாலாஜி நாராயணன்) >>>> <[email protected]> wrote: >>>> >>>>> Are you running balancer? If balancer is running and if it is slow, try >>>>> increasing the balancer bandwidth >>>>> >>>>> >>>>> On 24 March 2013 09:21, Tapas Sarangi <[email protected]> wrote: >>>>> Thanks for the follow up. I don't know whether attachment will pass >>>>> through this mailing list, but I am attaching a pdf that contains the >>>>> usage of all live nodes. >>>>> >>>>> All nodes starting with letter "g" are the ones with smaller storage >>>>> space where as nodes starting with letter "s" have larger storage space. >>>>> As you will see, most of the "gXX" nodes are completely full whereas >>>>> "sXX" nodes have a lot of unused space. >>>>> >>>>> Recently, we are facing crisis frequently as 'hdfs' goes into a mode >>>>> where it is not able to write any further even though the total space >>>>> available in the cluster is about 500 TB. We believe this has something >>>>> to do with the way it is balancing the nodes, but don't understand the >>>>> problem yet. May be the attached PDF will help some of you (experts) to >>>>> see what is going wrong here... >>>>> >>>>> Thanks >>>>> ------ >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>>> >>>>>> Balancer know about topology,but when calculate balancing it operates >>>>>> only with nodes not with racks. >>>>>> You can see how it work in Balancer.java in BalancerDatanode about >>>>>> string 509. >>>>>> >>>>>> I was wrong about 350Tb,35Tb it calculates in such way : >>>>>> >>>>>> For example: >>>>>> cluster_capacity=3.5Pb >>>>>> cluster_dfsused=2Pb >>>>>> >>>>>> avgutil=cluster_dfsused/cluster_capacity*100=57.14% used cluster capacity >>>>>> Then we know avg node utilization (node_dfsused/node_capacity*100) >>>>>> .Balancer think that all good if avgutil >>>>>> +10>node_utilizazation>=avgutil-10. >>>>>> >>>>>> Ideal case that all node used avgutl of capacity.but for 12TB node its >>>>>> only 6.5Tb and for 72Tb its about 40Tb. >>>>>> >>>>>> Balancer cant help you. >>>>>> >>>>>> Show me http://namenode.rambler.ru:50070/dfsnodelist.jsp?whatNodes=LIVE >>>>>> if you can. >>>>>> >>>>>> >>>>>> >>>>>> >>>>>>> In ideal case with replication factor 2 ,with two nodes 12Tb and 72Tb >>>>>>> you will be able to have only 12Tb replication data. >>>>>> >>>>>> Yes, this is true for exactly two nodes in the cluster with 12 TB and 72 >>>>>> TB, but not true for more than two nodes in the cluster. >>>>>> >>>>>>> >>>>>>> Best way,on my opinion,it is using multiple racks.Nodes in rack must be >>>>>>> with identical capacity.Racks must be identical capacity. >>>>>>> For example: >>>>>>> >>>>>>> rack1: 1 node with 72Tb >>>>>>> rack2: 6 nodes with 12Tb >>>>>>> rack3: 3 nodes with 24Tb >>>>>>> >>>>>>> It helps with balancing,because dublicated block must be another rack. >>>>>>> >>>>>> >>>>>> The same question I asked earlier in this message, does multiple racks >>>>>> with default threshold for the balancer minimizes the difference between >>>>>> racks ? >>>>>> >>>>>>> Why did you select hdfs?May be lustre,cephfs and other is better >>>>>>> choise. >>>>>> >>>>>> It wasn't my decision, and I probably can't change it now. I am new to >>>>>> this cluster and trying to understand few issues. I will explore other >>>>>> options as you mentioned. >>>>>> >>>>>> -- >>>>>> http://balajin.net/blog >>>>>> http://flic.kr/balajijegan >>>> >>>> >>>> >>>> >>>> -- >>>> http://balajin.net/blog >>>> http://flic.kr/balajijegan >>> >>> >> >> >
