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From Todd Lipcon <t...@cloudera.com>
Subject Re: HDFS HA IO Fencing
Date Thu, 25 Oct 2012 13:08:06 GMT
Hi Liu,

Locks are not sufficient, because there is no way to enforce a lock in a
distributed system without unbounded blocking. What you might be referring
to is a lease, but leases are still problematic unless you can put bounds
on the speed with which clocks progress on different machines, _and_ have
strict guarantees on the way each node's scheduler works. With Linux and
Java, the latter is tough.

You may want to look into QuorumJournalManager which doesn't require
setting up IO fencing.


On Thu, Oct 25, 2012 at 1:27 AM, lei liu <liulei412@gmail.com> wrote:

> I want to use HDFS HA function, I find the  IO Fencing function is
> complex in hadoop2.0. I think we can use  file lock to implement the  IO
> Fencing function, I think that is simple.
> Thanks,
> LiuLei

Todd Lipcon
Software Engineer, Cloudera

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