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From "Segel, Mike" <mse...@navteq.com>
Subject Re: Hadoop Java Versions
Date Tue, 28 Jun 2011 01:54:13 GMT
That doesn't seem right.
In one of our test clusters (19 data nodes) we found that under heavy loads we were disk I/O
bound and not network bound. Of course YMMV depending on your ToR switch. If we had more than
4 disks per node, we would probably see the network being the bottleneck. What did you set
your bandwidth settings in the hdfs-site.xml? ( going from memory not sure of the exact setting...)

But the good news... Newer hardware will start to have 10GBe on the motherboard.

Sent from a remote device. Please excuse any typos...

Mike Segel

On Jun 27, 2011, at 7:11 PM, "Ryan Rawson" <ryanobjc@gmail.com> wrote:

> On the subject of gige vs 10-gige, I think that we will very shortly
> be seeing interest in 10gig, since gige is only 120MB/sec - 1 hard
> drive of streaming data.  Nodes with 4+ disks are throttled by the
> network.  On a small cluster (20 nodes), the replication traffic can
> choke a cluster to death.  The only way to fix quickly it is to bring
> that node back up.  Perhaps the HortonWorks guys can work on that.
> 
> -ryan
> 
> On Mon, Jun 27, 2011 at 4:38 AM, Steve Loughran <stevel@apache.org> wrote:
>> On 26/06/11 20:23, Scott Carey wrote:
>>> 
>>> 
>>> On 6/23/11 5:49 AM, "Steve Loughran"<stevel@apache.org>  wrote:
>>> 
>> 
>>>> what's your HW setup? #cores/server, #servers, underlying OS?
>>> 
>>> CentOS 5.6.
>>> 4 cores / 8 threads a server (Nehalem generation Intel processor).
>> 
>> 
>> that should be enough to find problems. I've just moved up to a 6-core 12
>> thread desktop and that found problems on some non-Hadoop code, which shows
>> that the more threads you have, and the faster the machines are, the more
>> your race conditions show up. With Hadoop the fact that you can have 10-1000
>> servers means that in a large cluster the probability of that race condition
>> showing up scales well.
>> 
>>> Also run a smaller cluster with 2x quad core Core 2 generation Xeons.
>>> 
>>> Off topic:
>>> The single proc Nehalem is faster than the dual core 2's for most use
>>> cases -- and much lower power.  Looking forward to single proc 4 or 6 core
>>> Sandy Bridge based systems for the next expansion -- testing 4 core vs 4
>>> core has these 30% faster than the Nehalem generation systems in CPU bound
>>> tasks and lower power.  Intel prices single socket Xeons so much lower
>>> than the Dual socket ones that the best value for us is to get more single
>>> socket servers rather than fewer dual socket ones (with similar processor
>>> to hard drive ratio).
>> 
>> Yes, in a large cluster the price of filling the second socket can compare
>> to a lot of storage, and TB of storage is more tangible. I guess it depends
>> on your application.
>> 
>> Regarding Sandy Bridge, I've no experience of those, but I worry that 10
>> Gbps is still bleeding edge, and shouldn't be needed for code with good
>> locality anyway; it is probably more cost effective to stay at 1Gbps/server,
>> though the issue there is the #of HDD/s server generates lots of replication
>> traffic when a single server fails...
>> 


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