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From Zhe Zhang <...@apache.org>
Subject Re: HDFS Balancer - Balancing Effectively ?
Date Thu, 11 Aug 2016 17:49:53 GMT
Thanks Nicholas for the pointers; the first 2 links are not working.

On Thu, Aug 11, 2016 at 10:09 AM Tsz Wo Sze <szetszwo@yahoo.com.invalid>
wrote:

> Hi Senthi
> The Balancer performance was improved dramatically recently [1].  I am not
> sure if you know about the new conf and parameters; see [2].  If you are
> interested in more details on how the Balancer works, please see [3].
> Thanks.
> 1.
> https://community.hortonworks.com/content/kbentry/43615/hdfs-balancer-1-100x-performance-improvement.html2
> .
> https://community.hortonworks.com/content/kbentry/43849/hdfs-balancer-2-configurations-cli-options.html3
> .
> https://community.hortonworks.com/content/kbentry/44148/hdfs-balancer-3-cluster-balancing-algorithm.html
> Regards,Tsz-Wo
>
>     On Thursday, August 11, 2016 6:21 AM, Senthil Kumar <
> senthilec566@gmail.com> wrote:
>
>
>
>  Hi Team ,  Pls add your suggestion(s) here , So that i can tune parameters
> to balance cluster which is in bad shape now :( ..
>
>
> --Senthil
>
> On Thu, Aug 11, 2016 at 3:51 PM, Senthil Kumar <senthilec566@gmail.com>
> wrote:
>
> > Thanks Lars for your quick response!
> >
> > Here is my Cluster Utilization..
> > DFS Used% : 74.39%
> > DFS Remaining% : 25.60%
> >
> >
> > Block Pool Used% : 74.39%
> > DataNodes usages : Min % Median % Max % stdev %
> > 1.25% 99.72% 99.99% 22.53%
> > Hadoop Version : *2.4.1*
> >
> > Let's take an example :
> >
> >  Cluster  Live Nodes          :    1000
> >  Capacity Used 95-99%      :      700
> >  Capacity Used 90 -95 %    :      50
> >  Capacity Used  < 90 %    :      250
> >
> > I'm looking for an option to balance the data quickly from the nodes
> > category 90-95% to < 90% nodes category.. I know there is an option like
> > -include  & -exclude but it's not helping me ( or am i not using it
> > effectively ??  Pls advise here how to use these options properly if i
> want
> > to balance my cluster as described above ) .
> >
> > Is there any option like --force-balance ( include two other inputs like
> > force-balance-source-hosts(file) & force-balance-dest-hosts(file) )..
> > this way i believe we can achieve balancing in urgency mode when you have
> > 90% of nodes hitting  99% disk usage or when we have median 95% and above
> > .. Pls add your thoughts here ..
> >
> >
> > Here is the code that constructs the NW Topology by categorizing like
> > over-utilized , avg utilized and under-utilized .. Sometimes i could see
> > nodes with 70% of usage also comes under over-utilized ( tried with
> > threshold 10 - 30 ) . Correct me if anything wrong in my understanding.
> >
> > https://github.com/apache/hadoop/tree/release-2.4.1/
> > hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/
> > hadoop/hdfs/server/balancer
> >
> > */*create network topology and all data node lists: *
> > *    * overloaded, above-average, below-average, and underloaded*
> > *    * we alternates the accessing of the given datanodes array either
> by*
> > *    * an increasing order or a decreasing order.*
> > *    */  *
> > *    long overLoadedBytes = 0L, underLoadedBytes = 0L;*
> > *    for (DatanodeInfo datanode : DFSUtil.shuffle(datanodes)) {*
> > *      if (datanode.isDecommissioned() ||
> > datanode.isDecommissionInProgress()) {*
> > *        continue; // ignore decommissioning or decommissioned nodes*
> > *      }*
> > *      cluster.add(datanode);*
> > *      BalancerDatanode datanodeS;*
> > *      final double avg = policy.getAvgUtilization();*
> > *      if (policy.getUtilization(datanode) > avg) {*
> > *        datanodeS = new Source(datanode, policy, threshold);*
> > *        if (isAboveAvgUtilized(datanodeS)) {*
> > *          this.aboveAvgUtilizedDatanodes.add((Source)datanodeS);*
> > *        } else {*
> > *          assert(isOverUtilized(datanodeS)) :*
> > *            datanodeS.getDisplayName()+ "is not an overUtilized node";*
> > *          this.overUtilizedDatanodes.add((Source)datanodeS);*
> > *          overLoadedBytes += (long)((datanodeS.utilization-avg*
> > *              -threshold)*datanodeS.datanode.getCapacity()/100.0);*
> > *        }*
> > *      } else {*
> > *        datanodeS = new BalancerDatanode(datanode, policy, threshold);*
> > *        if ( isBelowOrEqualAvgUtilized(datanodeS)) {*
> > *          this.belowAvgUtilizedDatanodes.add(datanodeS);*
> > *        } else {*
> > *          assert isUnderUtilized(datanodeS) : "isUnderUtilized("*
> > *              + datanodeS.getDisplayName() + ")=" +
> > isUnderUtilized(datanodeS)*
> > *              + ", utilization=" + datanodeS.utilization; *
> > *          this.underUtilizedDatanodes.add(datanodeS);*
> > *          underLoadedBytes += (long)((avg-threshold-*
> > *
> > datanodeS.utilization)*datanodeS.datanode.getCapacity()/100.0);*
> > *        }*
> > *      }*
> > *      datanodeMap.put(datanode.getDatanodeUuid(), datanodeS);*
> > *    }*
> >
> >
> > Could someone help me here to understand the balancing policy and what
> are
> > the different parameters should i use to balance ( bring down median )
> > cluster ??
> >
> > --Senthil
> >
> > On Wed, Aug 10, 2016 at 8:21 PM, Lars Francke <lars.francke@gmail.com>
> > wrote:
> >
> >> Hi Senthil,
> >>
> >> I'm not sure I fully understand.
> >>
> >> If you're using a threshold of 30 that means you have a range of 60%
> that
> >> the balancer would consider to be okay.
> >>
> >> Example: The used space divided by your total available space in the
> >> cluster is 80% Then with a 30% threshold the balancer would try to bring
> >> all nodes within the range of 50-100% utilisation.
> >>
> >> The default threshold is 10% and that's a fairly huge range still
> >> especially on clusters that are almost at capacity. So a threshold of 5
> or
> >> even lower might work for you.
> >>
> >> What is your utilisation in the cluster (used space / available space)?
> >>
> >> Cheers,
> >> Lars
> >>
> >> On Wed, Aug 10, 2016 at 3:27 PM, Senthil Kumar <senthilec566@gmail.com>
> >> wrote:
> >>
> >>> Hi Team ,  We are running big cluster ( 3000 nodes cluster ) , many
> time
> >>> we
> >>> are hitting  Median Increasing to 99.99 % ( 80 % of the DN's ) .
> >>> Balancer
> >>> is running all time in cluster ..But still  median is not coming down
> >>> i.e <
> >>> 90 % ..
> >>>
> >>> Here is how i start balancer ?
> >>> /apache/hadoop/sbin/start-balancer.sh
> >>> -Ddfs.balance.bandwidthPerSec=104857600  *-threshold  30*
> >>>
> >>> What the recommended value for thershold ??  Is there any way to pass
> >>> param
> >>> only to move blocks from Over Utilized ( 98-100%) to under utilized ?
> >>>
> >>>
> >>> Pls advise!
> >>>
> >>>
> >>>
> >>>
> >>> Regards,
> >>> Senthil
> >>>
> >>
> >>
> >
>
>
>
>

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