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From Deepak Goel <deic...@gmail.com>
Subject Re: Reliability of Hadoop
Date Fri, 27 May 2016 19:41:34 GMT
Sorry once again if I am wrong, or my comments are without significance

I am not saying Hadoop is bad or good...It is just that Hadoop might be
indirectly encouraging commodity hardware and software to be developed
which is convenient but might not be very good (also the cost factor is
unproven with no proper case studies or whitepaper)

It is like the fast food industry, which is very convenient (a commodity)
but causing obesity all over the world (And hence also causing many
illness, poor health, social trauma therefore the cost of a burger to
anyone is actually far more than what a company charges when you eat it)

In effect what Hadoop (and all the other commercial software around it) is
saying that its ok if you have bad software (Application, JVM, OS), I will
provide another software which will hide all the problems of yours... We
might all just go the obesity way in the software industry too



Hey

Namaskara~Nalama~Guten Tag~Bonjour


   --
Keigu

Deepak
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www.simtree.net, deepak@simtree.net
deicool@gmail.com

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On Sat, May 28, 2016 at 12:51 AM, J. Rottinghuis <jrottinghuis@gmail.com>
wrote:

> We run several clusters of thousands of nodes (as do many companies), our
> largest one has over 10K nodes. Disks, machines, memory, and network fail
> all the time. The larger the scale, the higher the odds that some machine
> is bad in a given day. On the other hand, scale helps. If a single node our
> of 10K fails, 9,999 others participate in re-distributing state. Even a
> rack failure isn't a big deal most of the time (plus typically a rack fails
> due to a TOR issue, so the data is offline, but typically not lost
> permanently).
>
> Hadoop is designed to deal with this, and by-and-large it does. Critical
> components (such as Namenodes) can be configured to run in an HA pair with
> automatic failover. There is quite a bit of work going on by many in the
> Hadoop community to keep pushing the boundaries of scale.
>
> A node or a rack failing in a large cluster actually has less impact than
> at smaller scale. With a 5-node cluster, if 1 machine crashes you've taken
> 20% capacity (disk and compute) offline. 1 out of 1K barely registers.
> Ditto with a 3 rack cluster. Loose a rack and 1/3rd of your capacity is
> offline.
>
> It is large-scale coordinated failure you should worry about. Think
> several rows of racks coming offline due to power failure, a DC going
> offline due to fire in the building etc. Those are hard to deal with in
> software within a single DC. They should also be more rare, but as many
> companies have experienced, large scale coordinated failures do
> occasionally happen.
>
> As to your question in the other email thread, it is a well-established
> pattern that scaling horizontally with commodity hardware (and letting
> software such as Hadoop deal with failures) help with both scale and
> reducing cost.
>
> Cheers,
>
> Joep
>
>
> On Fri, May 27, 2016 at 11:02 AM, Arun Natva <arun.natva@gmail.com> wrote:
>
>> Deepak,
>> I have managed clusters where worker nodes crashed, disks failed..
>> HDFS takes care of the data replication unless you loose too many of the
>> nodes where there is not enough space to fit the replicas.
>>
>>
>>
>> Sent from my iPhone
>>
>> On May 27, 2016, at 11:54 AM, Deepak Goel <deicool@gmail.com> wrote:
>>
>>
>> Hey
>>
>> Namaskara~Nalama~Guten Tag~Bonjour
>>
>> We are yet to see any server go down in our cluster nodes in the
>> production environment? Has anyone seen reliability problems in their
>> production environment? How many times?
>>
>> Thanks
>> Deepak
>>    --
>> Keigu
>>
>> Deepak
>> 73500 12833
>> www.simtree.net, deepak@simtree.net
>> deicool@gmail.com
>>
>> LinkedIn: www.linkedin.com/in/deicool
>> Skype: thumsupdeicool
>> Google talk: deicool
>> Blog: http://loveandfearless.wordpress.com
>> Facebook: http://www.facebook.com/deicool
>>
>> "Contribute to the world, environment and more :
>> http://www.gridrepublic.org
>> "
>>
>>
>

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