Re: Understanding I/O behaviour - next try


--- Chuck Ebbert <cebbert@xxxxxxxxxx> wrote:

On 08/28/2007 11:53 AM, Martin Knoblauch wrote:

The basic setup is a dual x86_64 box with 8 GB of memory. The
DL380
has a HW RAID5, made from 4x72GB disks and about 100 MB write
cache.
The performance of the block device with O_DIRECT is about 90
MB/sec.

The problematic behaviour comes when we are moving large files
through
the system. The file usage in this case is mostly "use once" or
streaming. As soon as the amount of file data is larger than 7.5
GB, we
see occasional unresponsiveness of the system (e.g. no more ssh
connections into the box) of more than 1 or 2 minutes (!) duration
(kernels up to 2.6.19). Load goes up, mainly due to pdflush threads
and
some other poor guys being in "D" state.

Try booting with "mem=4096M", "mem=2048M", ...



hmm. I tried 1024M a while ago and IIRC did not see a lot [any]
difference. But as it is no big deal, I will repeat it tomorrow.

Just curious - what are you expecting? Why should it help?

Thanks
Martin


------------------------------------------------------
Martin Knoblauch
email: k n o b i AT knobisoft DOT de
www: http://www.knobisoft.de
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