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From Patrick Hunt <ph...@apache.org>
Subject Re: forceSync=no
Date Sat, 16 Jun 2012 00:27:15 GMT
Was that back when forceSync was broken? ;-) (seriously)

Patrick

On Fri, Jun 15, 2012 at 3:27 PM, Mahadev Konar <mahadev@hortonworks.com> wrote:
> Raj,
>  Are you seeing any perf improvements by using that setting? I had run
> some benchmarks and didnt find much improvement even if I did
> forceSync = no.
>
> thanks
> mahadev
>
> On Fri, Jun 15, 2012 at 12:45 PM, Raj N <raj.cassandra@gmail.com> wrote:
>> Thanks Patrick. So back to my original question. Will forceSync=no cause a
>> zookeeper node to not start up cleanly if it crashed? It doesn't happen all
>> the time. But it happened to me once. I had to cleanup all the transaction
>> logs on all the nodes and then bring the nodes back up. For my use case I
>> can tolerate losing data in the worst case scenario since I can regenerate
>> all the data. But I should be able to tolerate a single point of failure as
>> long as the node comes back up cleanly. Can zookeeper recover from a
>> corrupt transaction log using existing snapshots and then replaying
>> messages from its peers?
>>
>> Thanks
>> -Raj
>>
>> On Fri, Jun 15, 2012 at 2:17 PM, Patrick Hunt <phunt@apache.org> wrote:
>>
>>> For a single node failure I believe so.
>>>
>>> Patrick
>>>
>>> On Thu, Jun 14, 2012 at 11:56 AM, Raj N <raj.cassandra@gmail.com> wrote:
>>> > Sorry, I should have been more specific. By corrupt, I mean that the
>>> > zookeeper node doesn't come back up on a restart. I would have imagined
>>> > that zookeeper would sync the lost transactions from its peers. I agree
I
>>> > will have a problem if I have multiple failures. But for a single node
>>> > failure in a 3-node ensemble, I should be able to recover even if
>>> > forceSync=no.
>>> >
>>> > Thanks
>>> > -Raj
>>> >
>>> > On Thu, Jun 14, 2012 at 1:03 PM, Jonathan Simms <slyphon@gmail.com>
>>> wrote:
>>> >
>>> >> There's a big warning in the documentation that says that's a
>>> possibility.
>>> >> If you don't force both Java and the OS to flush their IO buffers to
>>> disk,
>>> >> then you have no guarantees that your data is consistent.
>>> >>
>>> >> On 6/14/12 10:56 AM, "Raj N" <raj.cassandra@gmail.com> wrote:
>>> >>
>>> >> >Are you guys aware of any issues with forceSync=no that could cause
the
>>> >> >transaction log to get corrupted on a zookeeper crash.
>>> >> >
>>> >> >Thanks
>>> >> >-Raj
>>> >>
>>> >>
>>> >>
>>>

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