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From Steve Loughran <ste...@apache.org>
Subject Re: Hadoop Java Versions
Date Mon, 27 Jun 2011 11:38:47 GMT
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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