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From Josh Elser <>
Subject Re: Accumulo defaults
Date Sat, 17 May 2014 22:17:27 GMT
And, one last thought, be careful about accidentally overriding walogs 
for the metadata table. There isn't ever a reason to turn off walogs for 
the metadata table (that I can think of).

I'm not sure if setting the table.walogs.enabled property in 
accumulo-site.xml would override the value that is initially configured 
on the metadata table or not. Hopefully not :)

On 5/17/14, 6:01 PM, Josh Elser wrote:
> Absolutely, if you restrict a problem, you can work around it in other
> ways. Not going to argue that.
> Since this is a user list though, I got very worried seeing something
> that roughly says "I'm benchmarking Accumulo with the WALs off". If
> you're providing resiliency against data lost using other tactics,
> that's fine, I just wanted to make sure that users who read this thread
> later don't think that running tests against Accumulo with the WALs off
> is "normal".
> Looking forward to see the full picture of the benchmarks!
> On 5/17/14, 5:27 PM, Jeremy Kepner wrote:
>> walog provides data loss protection in a specific set of circumstances.
>> Most of our deployments are under a different set of circumstances.
>> Accumulo is only one part of our systems and we have other
>> mechanisms for protecting against the loss of data.
>> We find the walog actually becomes a bottleneck in certain circumstances
>> and so turning it off increases the overall reliability of our system.
>> On Sat, May 17, 2014 at 04:27:29PM -0400, Josh Elser wrote:
>>> You're likely to lose data in *any* deployment with the walogs turned
>>> off.
>>> And, to reiterate what Sean says, I wouldn't really consider any
>>> benchmark with the walogs turned off valid except for "internal"
>>> benchmarks (ones where we evaluate components only within Accumulo
>>> for the sake of improving Accumulo itself and not comparing it to
>>> other systems).
>>> On 5/17/14, 3:30 PM, Sean Busbey wrote:
>>>> You can set both of those in the accumulo-site.xml.
>>>> However, it's going to be difficult to use benchmarks with walogs
>>>> disabled for valid comparisons to other systems. Also you are very
>>>> likely to lose data in any significantly sized deployment.
>>>> On Sat, May 17, 2014 at 1:35 PM, Kepner, Jeremy - 0553 - MITLL
>>>> < <>> wrote:
>>>>     As part of our Accumulo benchmarking we have decided to set certain
>>>>     values as defaults for all our databases:
>>>>              tserver.compaction.minor.concurrent.max=5
>>>>              table.walog.enabled=false
>>>>     We were wondering which file(s) we would need to modify to apply
>>>>     these defaults?
>>>> --
>>>> Sean

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