[Beowulf] Building new cluster - estimate
landman at scalableinformatics.com
Mon Aug 4 18:02:17 EDT 2008
Matt Lawrence wrote:
> On Mon, 4 Aug 2008, Joe Landman wrote:
>> This mirrors our experience, though RHEL stability under intense loads
>> is questionable IMO (talking about the kernel BTW). We find that the
>> missing drivers, the omitted drivers, the backported drivers along
>> with some odd and often useless "features" (4k stacks anyone?) render
>> the RHEL default kernels (and by definition the Centos kernels) less
>> useful for HPC and storage tasks than what we build. Our current
>> standard is a 18.104.22.168 kernel which is rock solid under load.
>> Working on a 2.6.26 based version now (even though I am on
>> vacation/holiday, I just updated it to 22.214.171.124 to address an observed
>> crashing issue with the RDMA server)
> Since I plan to continue running CentOS, it sounds like building a much
> later kernel rpm is the way I want to approach the problem. Will going
> to a much later kernel break any of the utilities? Other problems I can
> expect to see?
Doesn't break most things. We usually insert a new RPM and off it goes.
> What do you recommend for the kernel config?
>> Combine this with the small upper limit of ext3 partition sizes, the
>> file size limits in ext3, the serialization in the journaling code
>> (ext4 is extents based to help deal with this), ext3 just doesn't make
>> much sense in a storage/HPC system (apart from possibly boot/root file
>> system where performance is less critical). Yeah I have seen studies
>> from folks whom had done 1E6 removes, file creates, and other things
>> who claim xfs is slower than ext3. Yeah, those are bad benchmarks in
>> that they really don't touch on real end user use cases for the most
>> part (apart from possible large scale mail servers and other things
>> like that).
> I have never had any problems with ext3. I had dinner with a friend who
> is an expert Linux sysadmin who was warning me to stay away from xfs.
> He cited lots of fragmentation problems that routinely locked up his
> systems. I am willing to be convinced otherwise, but he is a very sharp
I haven't seen or heard anyone claim xfs 'routinely locks up their
system'. I won't comment on your friends "sharpness". I will point out
that several very large data stores/large cluster sites use xfs. By
definition, no large data store can be built with ext3 (16 TB limit with
patches, 8 TB in practice), so if your sharp friend is advising you to
do this ...
Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics LLC,
email: landman at scalableinformatics.com
web : http://www.scalableinformatics.com
phone: +1 734 786 8423
fax : +1 734 786 8452
cell : +1 734 612 4615
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