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From Ryan Rawson <ryano...@gmail.com>
Subject Re: Hadoop Java Versions
Date Tue, 28 Jun 2011 02:33:28 GMT
There are no bandwidth limitations in 0.20.x.  None that I saw at
least.  It was basically bandwidth-management-by-pwm.  You could
adjust the frequency of how many files-per-node were copied.

In my case, the load was HBase real time serving, so it was servicing
more smaller random reads, not a map-reduce. Everyone has their own
use case :-)


On Mon, Jun 27, 2011 at 6:54 PM, Segel, Mike <msegel@navteq.com> wrote:
> 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
> 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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