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From Scott Carey <sc...@richrelevance.com>
Subject Re: Hadoop Java Versions
Date Sun, 26 Jun 2011 19:23:45 GMT

On 6/23/11 5:49 AM, "Steve Loughran" <stevel@apache.org> wrote:

>On 22/06/2011 21:27, Scott Carey wrote:
>> "Problems have been reported with Hadoop, the 64-bit JVM and Compressed
>> Object References (the -XX:+UseCompressedOops option), so use of that
>> option is discouraged."
>> I think the above is dated.  It also lacks critical information. What
>> and OS version was the problem seen?
>A colleague saw it, intermittent JVM crashes. Unless he's updated I
>can't say the problem has gone away.
>> CompressedOops had several issues prior to Jre 6u20, and a few minor
>> were fixed in u21.  FWIW, I now exclusively use 64 bit w/ CompressedOops
>> for all Hadoop and non-Hadoop apps and have seen no issues.  It is the
>> default in 6u24 and 6u25 on a 64 bit  JVM.
>what's your HW setup? #cores/server, #servers, underlying OS?

CentOS 5.6.  
4 cores / 8 threads a server (Nehalem generation Intel processor).

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).  We are power constrained per rack either way.

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