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From Lars Francke <lars.fran...@gmail.com>
Subject Re: BlockPlacementPolicy question with hierarchical topology
Date Thu, 11 Jul 2019 08:54:13 GMT
Hi Takanobu,

sorry for the late reply, I missed your email.

That looks good, I'll take a look at that.

Cheers,
Lars

On Fri, Jul 5, 2019 at 6:47 AM Takanobu Asanuma <tasanuma@yahoo-corp.jp>
wrote:

> Hi Lars,
>
> I investigated it further. BlockPlacementPolicyWithNodeGroup may achieve
> your goal.
>
> https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockPlacementPolicyWithNodeGroup.java
>
> I don't have any experience of this placement policy, but found a use case
> slide from CACIB.
>
> https://www.slideshare.net/Hadoop_Summit/disaster-recovery-experience-at-cacib-hardening-hadoop-for-critical-financial-applications
>
> Thanks,
> - Takanobu
>
> ________________________________________
> From: Takanobu Asanuma <tasanuma@yahoo-corp.jp>
> Sent: Thursday, July 4, 2019 8:29:23 PM
> To: Lars Francke
> Cc: hdfs-user@hadoop.apache.org
> Subject: Re: BlockPlacementPolicy question with hierarchical topology
>
> Oh, you are right. It doesn't meet your needs. Sorry for the confusion.
> Seems it may be difficult to achive it with the existing policies.
>
> - Takanobu
>
> ________________________________________
> From: Lars Francke <lars.francke@gmail.com>
> Sent: Thursday, July 4, 2019 7:53:35 PM
> To: 浅沼 孝信
> Cc: hdfs-user@hadoop.apache.org
> Subject: Re: BlockPlacementPolicy question with hierarchical topology
>
> Hi Takanobu,
>
> thanks for the quick reply. I missed that class.
>
> But does it really do what I need?
> If I have these racks:
> /dc1/rack1
> /dc1/rack2
> /dc1/rack3
> /dc2/rack1
> /dc2/rack2
> /dc2/rack3
>
> And I place a single block in HDFS, couldn't this policy chose /dc1/rack1,
> /dc1/rack2, /dc1/rack3 at random?
>
> Cheers,
> Lars
>
> On Thu, Jul 4, 2019 at 12:46 PM Takanobu Asanuma <tasanuma@yahoo-corp.jp
> <mailto:tasanuma@yahoo-corp.jp>> wrote:
> Hi Lars,
>
> I think BlockPlacementPolicyRackFaultTolerant can do it.
> This policy tries to place 3 replica separately in different racks.
>
> <property>
>   <name>dfs.block.replicator.classname</name>
>
> <value>org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyRackFaultTolerant</value>
> </property>
>
> See also:
>
> https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockPlacementPolicyRackFaultTolerant.java
>
> Thanks,
> - Takanobu
> ________________________________________
> From: Lars Francke <lars.francke@gmail.com<mailto:lars.francke@gmail.com>>
> Sent: Thursday, July 4, 2019 18:15
> To: hdfs-user@hadoop.apache.org<mailto:hdfs-user@hadoop.apache.org>
> Subject: BlockPlacementPolicy question with hierarchical topology
>
> Hi,
>
> I have a customer who wants to make sure that copies of his data are
> distributed amongst datacenters. So they are using rack names like this
> /dc1/rack1, /dc1/rack2, /dc2/rack1 etc.
>
> Unfortunately, the BlockPlacementPolicyDefault seems to place all blocks
> on /dc1/* sometimes.
>
> Is there a way to guarantee that /dc1/* and /dc2/* will be used in this
> scenario?
>
> Looking at chooseRandomWithStorageTypeTwoTrial it seems to consider the
> full "scope" and not its components. I couldn't find anything in the code
> but I had hoped I'm missing something: Is there a way to configure HDFS for
> the behaviour I'd like?
>
> Thanks!
>
> Lars
>
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