http://bugzilla.novell.com/show_bug.cgi?id=507457
User michael.henninghaus@cae.de added comment
http://bugzilla.novell.com/show_bug.cgi?id=507457#c4
--- Comment #4 from Michael Henninghaus 2009-07-20 03:22:40 MDT ---
Steps to reproduce:
- Create a NFS-Server-Directory on a system and export it
- Implement a NFS-Client on the system
- Mount the nfs-directory f.e. in /home/<user>
- try to create testfiles (time dd if=/dev/zero of=/home/<user>/nfs/tesfile
bs=16k count=4096)
You'll see taht on this system the nfs-performance is very slow.
Writing this file to a normal directory on the hdd the performance is about 99
MB/s.
Writing the file to the local mounted NFS the performance is down to 19MB/s
(sync-option, 55MB/s if async)
During the write the cpu-waits are at 70-90%
The problem ist on this machine, network you don't have to use (connection
between two pc's) to reproduce this behavior.
We tried every tuning parameter, we set the io-scheduler to as (elevator=as at
boot-Time) but all these changes have no effect
Where ist the problem?
Is the sync option sooooo slow? Why is it so slow?
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