Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Threaded View
HDFS >> mail # user >> question about ZKFC daemon


Copy link to this message
-
Re: question about ZKFC daemon
Hi Craig,

I´m a bit confused, I have read this from cloudera:
https://ccp.cloudera.com/display/CDH4DOC/Hardware+Configuration+for+Quorum-based+Storage

The JournalNode daemon is relatively lightweight, so these daemons can
reasonably be collocated on machines with other Hadoop daemons, for example
NameNodes, the JobTracker, or the YARN ResourceManager.
Cloudera recommends that you deploy the JournalNode daemons on the "master"
host or hosts (NameNode, Standby NameNode, JobTracker, etc.) so the
JournalNodes' local directories can use the reliable local storage on those
machines.
There must be at least three JournalNode daemons, since edit log
modifications must be written to a majority of JournalNodes
as you can read they recommend to put journalnode daemons with the
namenodes, but you say the opposite.??¿?¿??
Thanks for your answer,

ESGLinux,
2012/12/28 Craig Munro <[EMAIL PROTECTED]>

> You need the following:
>
> - active namenode + zkfc
> - standby namenode + zkfc
> - pool of journal nodes (odd number, 3 or more)
> - pool of zookeeper nodes (odd number, 3 or more)
>
> As the journal nodes hold the namesystem transactions they should not be
> co-located with the namenodes in case of failure.  I distribute the journal
> and zookeeper nodes across the hosts running datanodes or as Harsh says you
> could co-locate them on dedicated hosts.
>
> ZKFC does not monitor the JobTracker.
>
> Regards,
> Craig
> On Dec 28, 2012 9:25 AM, "ESGLinux" <[EMAIL PROTECTED]> wrote:
>
>> Hi,
>>
>> well, If I have understand you I can configure my NN HA cluster this way:
>>
>> - Active NameNode + 1 ZKFC daemon + Journal Node
>> - Standby NameNode + 1 ZKFC daemon + Journal Node
>> - JobTracker node + 1 ZKFC daemon + Journal Node,
>>
>> Is this right?
>>
>> Thanks in advance,
>>
>> ESGLinux,
>>
>> 2012/12/27 Harsh J <[EMAIL PROTECTED]>
>>
>>> Hi,
>>>
>>> There are two different things here: Automatic Failover and Quorum
>>> Journal Manager. The former, used via a ZooKeeper Failover Controller,
>>> is to manage failovers automatically (based on health checks of NNs).
>>> The latter, used via a set of Journal Nodes, is a medium of shared
>>> storage for namesystem transactions that helps enable HA.
>>>
>>> In a typical deployment, you want 3 or more (odd) JournalNodes for
>>> reliable HA, preferably on nodes of their own if possible (like you
>>> would for typical ZooKeepers, and you may co-locate with those as
>>> well) and one ZKFC for each NameNode (connected to the same ZK
>>> quorum).
>>>
>>> On Thu, Dec 27, 2012 at 5:33 PM, ESGLinux <[EMAIL PROTECTED]> wrote:
>>> > Hi all,
>>> >
>>> > I have a doubt about how to deploy the Zookeeper in a NN HA  cluster,
>>> >
>>> > As far as I know, I need at least three nodes to run three ZooKeeper
>>> > FailOver Controller (ZKFC). I plan to put these 3 daemons this way:
>>> >
>>> > - Active NameNode + 1 ZKFC daemon
>>> > - Standby NameNode + 1 ZKFC daemon
>>> > - JobTracker node + 1 ZKFC daemon, (is this right?)
>>> >
>>> > so the quorum is formed with these three nodes. The nodes that runs a
>>> > namenode are right because the ZKFC monitors it, but what does the
>>> third
>>> > daemon?
>>> >
>>> > as I read from this url:
>>> >
>>> https://ccp.cloudera.com/display/CDH4DOC/Software+Configuration+for+Quorum-based+Storage#SoftwareConfigurationforQuorum-basedStorage-AutomaticFailoverConfiguration
>>> >
>>> > this daemons are only related with NameNodes, (Health monitoring - the
>>> ZKFC
>>> > pings its local NameNode on a periodic basis with a health-check
>>> command.)
>>> > so what does the third ZKFC? I used the jobtracker node but I could use
>>> > another node without any daemon on it...
>>> >
>>> > Thanks in advance,
>>> >
>>> > ESGLInux,
>>> >
>>> >
>>> >
>>>
>>>
>>>
>>> --
>>> Harsh J
>>>
>>
>>