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From "Kevin O'dell" <kevin.od...@cloudera.com>
Subject Re: introducing nodes w/ more storage
Date Thu, 02 Apr 2015 12:41:16 GMT
Hi Mike,

  Sorry for the delay here.

How does the HDFS load balancer impact the load balancing of HBase? <-- The
HDFS load balancer is not automatically run, it is a manual process that is
kicked off. It is not recommended to *ever run the HDFS balancer on a
cluster running HBase.  Similar to have HBase has no concept or care about
the underlying storage, HDFS has no concept or care of the region layout,
nor the locality we worked so hard to build through compactions.

Furthermore, once the HDFS balancer has saved us from running out of space
on the smaller nodes, we will run a major compaction, and re-write all of
the HBase data right back to where it was before.

one is the number of regions managed by a region server that’s HBase’s
load, right? And then there’s the data distribution of HBase files that is
really managed by HDFS load balancer, right? <--- Right, until we run major
compaction and "restore" locality by moving the data back

Even still… eventually the data will be distributed equally across the
cluster. What’s happening with the HDFS balancer?  Is that heterogenous or
homogenous in terms of storage? <-- Not quite, as I said before the HDFS
balancer is manual, so it is quite easy to build up a skew, especially if
you use a datanode as an edge node or thrift gateway etc.  Yes, the HDFS
balancer is heterogenous, but it doesn't play nice with HBase.

*The use of the word ever should not be construed as a true definitive.
Ever is being used to represent a best practice.  In many cases the HDFS
balancer needs to be run, especially in multi-tenant clusters
with archive data.  It is best to immediately run a major compaction to
restore HBase locality if the HDFS balancer is used.

On Mon, Mar 23, 2015 at 10:50 AM, Michael Segel <michael_segel@hotmail.com>
wrote:

> @lars,
>
> How does the HDFS load balancer impact the load balancing of HBase?
>
> Of course there are two loads… one is the number of regions managed by a
> region server that’s HBase’s load, right?
> And then there’s the data distribution of HBase files that is really
> managed by HDFS load balancer, right?
>
> OP’s question is having a heterogenous cluster where he would like to see
> a more even distribution of data/free space based on the capacity of the
> newer machines in the cluster.
>
> This is a storage question, not a memory/cpu core question.
>
> Or am I missing something?
>
>
> -Mike
>
> > On Mar 22, 2015, at 10:56 PM, lars hofhansl <larsh@apache.org> wrote:
> >
> > Seems that it should not be too hard to add that to the stochastic load
> balancer.
> > We could add a spaceCost or something.
> >
> >
> >
> > ----- Original Message -----
> > From: Jean-Marc Spaggiari <jean-marc@spaggiari.org>
> > To: user <user@hbase.apache.org>
> > Cc: Development <Development@mentacapital.com>
> > Sent: Thursday, March 19, 2015 12:55 PM
> > Subject: Re: introducing nodes w/ more storage
> >
> > You can extend the default balancer and assign the regions based on
> > that.But at the end, the replicated blocks might still go all over the
> > cluster and your "small" nodes are going to be full and will not be able
> to
> > get anymore writes even for the regions they are supposed to get.
> >
> > I'm not sure there is a good solution for what you are looking for :(
> >
> > I build my own balancer but because of differences in the CPUs, not
> because
> > of differences of the storage space...
> >
> >
> > 2015-03-19 15:50 GMT-04:00 Nick Dimiduk <ndimiduk@gmail.com>:
> >
> >> Seems more fantasy than fact, I'm afraid. The default load balancer [0]
> >> takes store file size into account, but has no concept of capacity. It
> >> doesn't know that nodes in a heterogenous environment have different
> >> capacity.
> >>
> >> This would be a good feature to add though.
> >>
> >> [0]:
> >>
> >>
> https://github.com/apache/hbase/blob/branch-1.0/hbase-server/src/main/java/org/apache/hadoop/hbase/master/balancer/StochasticLoadBalancer.java
> >>
> >> On Tue, Mar 17, 2015 at 7:26 AM, Ted Tuttle <ted@mentacapital.com>
> wrote:
> >>
> >>> Hello-
> >>>
> >>> Sometime back I asked a question about introducing new nodes w/ more
> >>> storage that existing nodes.  I was told at the time that HBase will
> not
> >> be
> >>> able to utilize the additional storage; I assumed at the time that
> >> regions
> >>> are allocated to nodes in something like a round-robin fashion and the
> >> node
> >>> with the least storage sets the limit for how much each node can
> utilize.
> >>>
> >>> My question this time around has to do with nodes w/ unequal numbers of
> >>> volumes: Does HBase allocate regions based on nodes or volumes on the
> >>> nodes?  I am hoping I can add a node with 8 volumes totaling 8X TB and
> >> all
> >>> the volumes will be filled.  This even though legacy nodes have 5
> volumes
> >>> and total storage of 5X TB.
> >>>
> >>> Fact or fantasy?
> >>>
> >>> Thanks,
> >>> Ted
> >>>
> >>>
> >>
> >
>
> The opinions expressed here are mine, while they may reflect a cognitive
> thought, that is purely accidental.
> Use at your own risk.
> Michael Segel
> michael_segel (AT) hotmail.com
>
>
>
>
>
>


-- 
Kevin O'Dell
Field Enablement, Cloudera

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