What Kevin says.
The best we can do is exclude the HBase from the HDFS balancer (HDF S-6133).The
HDFS balancer will destroy data locality for HBase. If you don't care - maybe
you have a fat network tree, and your network bandwidth matches the aggregate
disk throughput for each machine - you can run it. Even then as Kevin says,
HBase will just happily rewrite it as before.
Balancing of HBase data has to happen on the HBase level. Then we have to
decide what we use as a basis for distribution.CPU? RAM? disk space? IOPs? disk
throughput? It depends... So some configurable function of those.
-- Lars
From: Kevin O'dell <[email protected]>
To: "[email protected]" <[email protected]>
Cc: lars hofhansl <[email protected]>
Sent: Thursday, April 2, 2015 5:41 AM
Subject: Re: introducing nodes w/ more storage
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 <[email protected]>
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 <[email protected]> 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 <[email protected]>
> To: user <[email protected]>
> Cc: Development <[email protected]>
> 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 <[email protected]>:
>
>> 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 <[email protected]> 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
