I am in the process of building out a clustered environment that is going to start very small but grow extremely fast. I am just trying to figure out the following:

1. How many master nodes can I have?

2. If the answers is only 1 what happens if the master fails or dies. Does a slave take over and if so is the slave just referenced in the master files?

Thanks for your help I am just trying to understand this before I order my equipment. The build out will be a couple master nodes for redundancy, 10 data nodes running HDFS AND HBASE and a 2 to 3 node zookeeper cluster. We anticipate that out cluster will grow to 80 nodes before years end which is why I am thinking of the setup they way I am if anyone has feedback for a different setup please let me know.  Also if there is a doc that covers that would be beneficial.

Thanks for everyones help I do appreciate it.

There is only one active HBase master at any given time, but there can be any number of backup masters.  The failover is automated and coordinated via ZooKeeper.  Regionservers and clients use ZooKeeper to determine who is the current active master.  You can run with as many as you want.

On larger clusters, I usually recommend around 5 master nodes.  One possible configuration is to have all 5 with ZK (running on their own dedicated spindles), one for the NameNode, one for the SecondaryNameNode, and the other three can be HMasters (one will be the normal HMaster, the other backups).

JG

> -----Original Message-----
> From: Joseph Coleman [mailto:[EMAIL PROTECTED]]
> Sent: Monday, February 07, 2011 11:05 AM
> To: [EMAIL PROTECTED]
> Subject: Master node Question
>
> I am in the process of building out a clustered environment that is going to
> start very small but grow extremely fast. I am just trying to figure out the
> following:
>
> 1. How many master nodes can I have?
>
> 2. If the answers is only 1 what happens if the master fails or dies. Does a
> slave take over and if so is the slave just referenced in the master files?
>
> Thanks for your help I am just trying to understand this before I order my
> equipment. The build out will be a couple master nodes for redundancy, 10
> data nodes running HDFS AND HBASE and a 2 to 3 node zookeeper cluster.
> We anticipate that out cluster will grow to 80 nodes before years end which is
> why I am thinking of the setup they way I am if anyone has feedback for a
> different setup please let me know.  Also if there is a doc that covers that
> would be beneficial.
>
> Thanks for everyones help I do appreciate it.

Thank you for the reply that is very helpful I assume this is also the
case for the HDFS master as well. Just list your masters  MasterA, MasterB
and MasterC in the masters config files and also have your 2 of the three
in the slaves as well I take it then execute your start commands from one
master only example MasterA.

On 2/7/11 1:29 PM, "Jonathan Gray" <[EMAIL PROTECTED]> wrote:

>There is only one active HBase master at any given time, but there can be
>any number of backup masters.  The failover is automated and coordinated
>via ZooKeeper.  Regionservers and clients use ZooKeeper to determine who
>is the current active master.  You can run with as many as you want.
>
>On larger clusters, I usually recommend around 5 master nodes.  One
>possible configuration is to have all 5 with ZK (running on their own
>dedicated spindles), one for the NameNode, one for the SecondaryNameNode,
>and the other three can be HMasters (one will be the normal HMaster, the
>other backups).
>
>JG
>
>> -----Original Message-----
>> From: Joseph Coleman [mailto:[EMAIL PROTECTED]]
>> Sent: Monday, February 07, 2011 11:05 AM
>> To: [EMAIL PROTECTED]
>> Subject: Master node Question
>>
>> I am in the process of building out a clustered environment that is
>>going to
>> start very small but grow extremely fast. I am just trying to figure
>>out the
>> following:
>>
>> 1. How many master nodes can I have?
>>
>> 2. If the answers is only 1 what happens if the master fails or dies.
>>Does a
>> slave take over and if so is the slave just referenced in the master
>>files?
>>
>> Thanks for your help I am just trying to understand this before I order
>>my
>> equipment. The build out will be a couple master nodes for redundancy,
>>10
>> data nodes running HDFS AND HBASE and a 2 to 3 node zookeeper cluster.
>> We anticipate that out cluster will grow to 80 nodes before years end
>>which is
>> why I am thinking of the setup they way I am if anyone has feedback for
>>a
>> different setup please let me know.  Also if there is a doc that covers
>>that
>> would be beneficial.
>>
>> Thanks for everyones help I do appreciate it.
>

Unfortunately, this is not the case for the HDFS NameNode.  HDFS does not support out-of-the-box backup master nodes.  There are a few different techniques people use for NameNode high availability... you should be able to find some stuff with a Google search, though none are especially simple.

In general, people run the NameNode on a more fault tolerant node... Dual PSUs, RAID, etc... I'd recommend at least mirrored RAID on the master nodes and dual power supplies.

JG

> -----Original Message-----
> From: Joseph Coleman [mailto:[EMAIL PROTECTED]]
> Sent: Monday, February 07, 2011 11:38 AM
> To: [EMAIL PROTECTED]
> Subject: Re: Master node Question
>
> Thank you for the reply that is very helpful I assume this is also the case for
> the HDFS master as well. Just list your masters  MasterA, MasterB and
> MasterC in the masters config files and also have your 2 of the three in the
> slaves as well I take it then execute your start commands from one master
> only example MasterA.
>
>
>
>
>
> On 2/7/11 1:29 PM, "Jonathan Gray" <[EMAIL PROTECTED]> wrote:
>
> >There is only one active HBase master at any given time, but there can
> >be any number of backup masters.  The failover is automated and
> >coordinated via ZooKeeper.  Regionservers and clients use ZooKeeper to
> >determine who is the current active master.  You can run with as many as
> you want.
> >
> >On larger clusters, I usually recommend around 5 master nodes.  One
> >possible configuration is to have all 5 with ZK (running on their own
> >dedicated spindles), one for the NameNode, one for the
> >SecondaryNameNode, and the other three can be HMasters (one will be
> the
> >normal HMaster, the other backups).
> >
> >JG
> >
> >> -----Original Message-----
> >> From: Joseph Coleman [mailto:[EMAIL PROTECTED]]
> >> Sent: Monday, February 07, 2011 11:05 AM
> >> To: [EMAIL PROTECTED]
> >> Subject: Master node Question
> >>
> >> I am in the process of building out a clustered environment that is
> >>going to  start very small but grow extremely fast. I am just trying
> >>to figure out the
> >> following:
> >>
> >> 1. How many master nodes can I have?
> >>
> >> 2. If the answers is only 1 what happens if the master fails or dies.
> >>Does a
> >> slave take over and if so is the slave just referenced in the master
> >>files?
> >>
> >> Thanks for your help I am just trying to understand this before I
> >>order my  equipment. The build out will be a couple master nodes for
> >>redundancy,
> >>10
> >> data nodes running HDFS AND HBASE and a 2 to 3 node zookeeper cluster.
> >> We anticipate that out cluster will grow to 80 nodes before years end
> >>which is  why I am thinking of the setup they way I am if anyone has
> >>feedback for a  different setup please let me know.  Also if there is
> >>a doc that covers that  would be beneficial.
> >>
> >> Thanks for everyones help I do appreciate it.
> >