FAQ
Hi,

I am setting up a simple hbase system. I currently have a 2 node
clsuter server for
the zookeeper servers ...

I read that zookeeper needs a simple majority to recover from failures.
So is 2 same as 1 as far as recovery goes? Does it help in load balancing.

If 1 of 2 goes down , does it affect the hbase tables? i,e if i install a new
zoo keeper server (replace) can i recover the tables?

thanks
ishwar

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  • Tatsuya Kawano at Nov 11, 2009 at 1:29 am
    hi ishwar,
    I read that zookeeper needs a simple majority to recover from failures.
    So is 2 same as 1 as far as recovery goes?
    Yes. When they lost contact with other (e.g. by a network disruption),
    they both stop serving because they can't say "I'm in the majority."

    Does it help in load balancing.
    I don't find a clear answer for this in ZK documents, but I found this
    JIRA says "Clients randomly connect to a server, which typically
    balances the number of sessions", so the answer should be yes.

    https://issues.apache.org/jira/browse/ZOOKEEPER-571

    If 1 of 2  goes down , does it affect the hbase tables? i,e if i install a new
    zoo keeper server (replace) can i recover the tables?
    When ZK ensemble becomes unavailable, HBase master and region servers
    think they are disconnected from the HBase cluster, so they shutdown
    gracefully. You shouldn't loose any data by this, but you have to
    start the HBase cluster again once ZK ensemble becomes available.


    Thanks,

    --
    Tatsuya Kawano (Mr.)
    Tokyo, Japan


    On Wed, Nov 11, 2009 at 9:34 AM, ishwar ramani wrote:
    Hi,

    I am setting up a simple hbase system. I currently have a 2 node
    clsuter server for
    the zookeeper servers ...

    I read that zookeeper needs a simple majority to recover from failures.
    So is 2 same as 1 as far as recovery goes? Does it help in load balancing.

    If 1 of 2  goes down , does it affect the hbase tables? i,e if i install a new
    zoo keeper server (replace) can i recover the tables?

    thanks
    ishwar
  • Ryan Rawson at Nov 11, 2009 at 1:32 am
    Another word on Zookeeper, at a recent presentation, the ZK guys said
    that yahoo was supporting thousands of clients from a 5 node cluster.
    Some of my numbers may be off, but a single node for a small cluster
    should be just fine.

    On Tue, Nov 10, 2009 at 5:28 PM, Tatsuya Kawano
    wrote:
    hi ishwar,
    I read that zookeeper needs a simple majority to recover from failures.
    So is 2 same as 1 as far as recovery goes?
    Yes. When they lost contact with other (e.g. by a network disruption),
    they both stop serving because they can't say "I'm in the majority."

    Does it help in load balancing.
    I don't find a clear answer for this in ZK documents, but I found this
    JIRA says "Clients randomly connect to a server, which typically
    balances the number of sessions", so the answer should be yes.

    https://issues.apache.org/jira/browse/ZOOKEEPER-571

    If 1 of 2  goes down , does it affect the hbase tables? i,e if i install a new
    zoo keeper server (replace) can i recover the tables?
    When ZK ensemble becomes unavailable, HBase master and region servers
    think they are disconnected from the HBase cluster, so they shutdown
    gracefully. You shouldn't loose any data by this, but you have to
    start the HBase cluster again once ZK ensemble becomes available.


    Thanks,

    --
    Tatsuya Kawano (Mr.)
    Tokyo, Japan


    On Wed, Nov 11, 2009 at 9:34 AM, ishwar ramani wrote:
    Hi,

    I am setting up a simple hbase system. I currently have a 2 node
    clsuter server for
    the zookeeper servers ...

    I read that zookeeper needs a simple majority to recover from failures.
    So is 2 same as 1 as far as recovery goes? Does it help in load balancing.

    If 1 of 2  goes down , does it affect the hbase tables? i,e if i install a new
    zoo keeper server (replace) can i recover the tables?

    thanks
    ishwar
  • Ryan Rawson at Nov 11, 2009 at 1:30 am
    Hi,

    Zookeeper is a 2N+1 system. 2 nodes is the same as 1, a single
    failure will take the system offline. You will need to deploy at
    least 3 nodes to get protection from 1 recovery. 3 to 5 nodes is a
    typical deployment scenario.

    If ZK goes down, you can expect a complete crash of hbase, which can
    potentially lose data due to not having HDFS-265. So you don't want
    that.

    If you dont have many nodes, running ZK 1 node on the master/namenode
    is probably fine. IF that node crashes, you'll be having HDFS
    problems anyways :-)

    -ryan

    On Tue, Nov 10, 2009 at 4:34 PM, ishwar ramani wrote:
    Hi,

    I am setting up a simple hbase system. I currently have a 2 node
    clsuter server for
    the zookeeper servers ...

    I read that zookeeper needs a simple majority to recover from failures.
    So is 2 same as 1 as far as recovery goes? Does it help in load balancing.

    If 1 of 2  goes down , does it affect the hbase tables? i,e if i install a new
    zoo keeper server (replace) can i recover the tables?

    thanks
    ishwar

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categorieshbase, hadoop
postedNov 11, '09 at 12:34a
activeNov 11, '09 at 1:32a
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