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HDFS >> mail # user >> Re: Estimating disk space requirements


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Jean-Marc Spaggiari 2013-01-18, 14:12
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Panshul Whisper 2013-01-18, 14:24
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Panshul Whisper 2013-01-18, 22:30
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Re: Estimating disk space requirements
It is usually better to not subdivide nodes into virtual nodes.  You will
generally get better performance form the original node because you only
pay for the OS once and because your disk I/O will be scheduled better.

If you look at EC2 pricing, however, the spot market often has arbitrage
opportunities where one size node is absurdly cheap relative to others.  In
that case, it pays to scale the individual nodes up or down.

The only reasonable reason to split nodes to very small levels is for
testing and training.

On Fri, Jan 18, 2013 at 2:30 PM, Panshul Whisper <[EMAIL PROTECTED]>wrote:

> Thnx for the reply Ted,
>
> You can find 40 GB disks when u make virtual nodes on a cloud like
> Rackspace ;-)
>
> About the os partitions I did not exactly understand what you meant.
> I have made a server on the cloud.. And I just installed and configured
> hadoop and hbase in the /use/local folder.
> And I am pretty sure it does not have a separate partition for root.
>
> Please help me explain what u meant and what else precautions should I
> take.
>
> Thanks,
>
> Regards,
> Ouch Whisper
> 01010101010
> On Jan 18, 2013 11:11 PM, "Ted Dunning" <[EMAIL PROTECTED]> wrote:
>
>> Where do you find 40gb disks now a days?
>>
>> Normally your performance is going to be better with more space but your
>> network may be your limiting factor for some computations.  That could give
>> you some paradoxical scaling.  Hbase will rarely show this behavior.
>>
>> Keep in mind you also want to allow for an os partition. Current standard
>> practice is to reserve as much as 100 GB for that partition but in your
>> case 10gb better:-)
>>
>> Note that if you account for this, the node counts don't scale as simply.
>>  The overhead of these os partitions goes up with number of nodes.
>>
>> On Jan 18, 2013, at 8:55 AM, Panshul Whisper <[EMAIL PROTECTED]>
>> wrote:
>>
>> If we look at it with performance in mind,
>> is it better to have 20 Nodes with 40 GB HDD
>> or is it better to have 10 Nodes with 80 GB HDD?
>>
>> they are connected on a gigabit LAN
>>
>> Thnx
>>
>>
>> On Fri, Jan 18, 2013 at 2:26 PM, Jean-Marc Spaggiari <
>> [EMAIL PROTECTED]> wrote:
>>
>>> 20 nodes with 40 GB will do the work.
>>>
>>> After that you will have to consider performances based on your access
>>> pattern. But that's another story.
>>>
>>> JM
>>>
>>> 2013/1/18, Panshul Whisper <[EMAIL PROTECTED]>:
>>> > Thank you for the replies,
>>> >
>>> > So I take it that I should have atleast 800 GB on total free space on
>>> > HDFS.. (combined free space of all the nodes connected to the
>>> cluster). So
>>> > I can connect 20 nodes having 40 GB of hdd on each node to my cluster.
>>> Will
>>> > this be enough for the storage?
>>> > Please confirm.
>>> >
>>> > Thanking You,
>>> > Regards,
>>> > Panshul.
>>> >
>>> >
>>> > On Fri, Jan 18, 2013 at 1:36 PM, Jean-Marc Spaggiari <
>>> > [EMAIL PROTECTED]> wrote:
>>> >
>>> >> Hi Panshul,
>>> >>
>>> >> If you have 20 GB with a replication factor set to 3, you have only
>>> >> 6.6GB available, not 11GB. You need to divide the total space by the
>>> >> replication factor.
>>> >>
>>> >> Also, if you store your JSon into HBase, you need to add the key size
>>> >> to it. If you key is 4 bytes, or 1024 bytes, it makes a difference.
>>> >>
>>> >> So roughly, 24 000 000 * 5 * 1024 = 114GB. You don't have the space to
>>> >> store it. Without including the key size. Even with a replication
>>> >> factor set to 5 you don't have the space.
>>> >>
>>> >> Now, you can add some compression, but even with a lucky factor of 50%
>>> >> you still don't have the space. You will need something like 90%
>>> >> compression factor to be able to store this data in your cluster.
>>> >>
>>> >> A 1T drive is now less than $100... So you might think about replacing
>>> >> you 20 GB drives by something bigger.
>>> >> to reply to your last question, for your data here, you will need AT
>>> >> LEAST 350GB overall storage. But that's a bare minimum. Don't go under
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Panshul Whisper 2013-01-18, 23:34