hbase-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Michael Segel <michael_se...@hotmail.com>
Subject Re: introducing nodes w/ more storage
Date Thu, 02 Apr 2015 14:33:16 GMT


When you say … "It is not recommended to *ever run the HDFS balancer on a cluster running
HBase. “ … thats a very scary statement.

Not really a good idea.  Unless you are building a cluster for a specific use case. 


When you look at the larger picture… in most use cases, the cluster will contain more data
in flat files (HDFS) than they would inside HBase.
(which you allude to in you last paragraph) so balancing is a good idea. (Even manual processes
can be run in cron jobs ;-) 

And no, you do not use a data node as an edge node. 
(Really saying that? C’mon, really? ) Never a good design. Ever. 


I agree that you should run major compactions after running the load balancer. (HDFS)
But the point I am trying to make is that with respect to HBase, you still need to think about
the cluster as a whole. 


> On Apr 2, 2015, at 7:41 AM, Kevin O'dell <kevin.odell@cloudera.com> wrote:
> 
> 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

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






Mime
View raw message