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From Ryan Rawson <ryano...@gmail.com>
Subject Re: Hadoop Java Versions
Date Tue, 28 Jun 2011 00:10:44 GMT
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.


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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