[Beowulf] Building new cluster - estimate
kyron at neuralbs.com
Wed Aug 6 21:07:01 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 188.8.131.52 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 184.108.40.206 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?
> 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 fellow.
Check the kernel mailing list for XFS problems with RAID5 if you use
mdadm...jsut a gentle suggestion ;)
> -- Matt
> It's not what I know that counts.
> It's what I can remember in time to use.
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