From: Rui Pedro Mendes Salgueiro <rps-G7wE2RHCdwNeoWH0uzbU5w@public.gmane.org>
Subject: [NFS] NFS performance problems
Date: Tue, 20 Nov 2007 17:53:56 +0000
Message-ID: <20071120175356.GA14445@dolly1.mat.uc.pt>
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Hello

I am not sure if this question is appropriate for this list, but since
I am been unable to find an answer elsewhere ...

For many years we have been using a network configuration in which a
NFS server has the home directories of our users and various computers
mount those file systems. For the past few years the server has been a
Suse linux system.

Our current NFS server is a 64-bit bi-processor (2 AMD Opteron(tm)
Processor 246).  It has 4 SATA disks, configured in 2 RAID-1 arrays.
Each of those has a ext3 filesystem.

This server has a some load constantly, because apart from the several
dozens computers accessing NFS or samba, our mail server is also using
it. So, each mail that arrives means an access to the .forward and
.procmailrc of the recipient. With the amount of spam that arrives here,
this means a constant load:

top - 15:50:56 up 20 days,  1:33,  9 users,  load average: 3.42, 2.95, 2.38

19200 geo0501   15   0 75076 5224 3480 S    2  0.1   0:07.94 smbd               
 2336 root      10  -5     0    0    0 S    1  0.0  57:07.70 kjournald          
 2334 root      10  -5     0    0    0 S    1  0.0  33:19.89 kjournald          
 2279 root      10  -5     0    0    0 S    0  0.0  15:10.98 md0_raid1          
 2283 root      10  -5     0    0    0 S    0  0.0  24:45.79 md1_raid1          
 3935 root      15   0     0    0    0 S    0  0.0  14:04.25 nfsd               
 3943 root      15   0     0    0    0 S    0  0.0  14:18.43 nfsd               
 3947 root      15   0     0    0    0 S    0  0.0  13:57.06 nfsd               
 8325 ed0127    15   0 75044 4812 3264 S    0  0.1   0:01.29 smbd               

This server  was installed with Suse 9.1 (linux 2.6.4-52, nfs-utils-1.0.6-103)
and worked well for a couple of years.
Then I had to upgrade it (since 9.1 was no longer being updated) and I
installed 10.1 (linux 2.6.18.8-0.7, nfs-utils-1.0.10-22).

This upgrade caused some serious performance problem (I suspect related
to locks).  The most obvious problem is that it can take a long time
for a KDE user to login (5 minutes or more !), when a number of users
login at the same time (e.g. a classroom with 16 students). KDE seems
to spend that time writing and rewriting files in ~/.kde/share/ .

I know that the problem is related to the change of version, because
I could boot the old system (it is still installed in another partition)
and than it worked well again. Samba doesn't seem to be affected, since
the windows users don't complain.

I tried to ask on the suse mailing list and newsgroup if someone else
had the same problem, or if someone had a similar setup working well,
but I didn't get any useful answer. 


I don't know what to do about this. Things I thought of trying:

 - install 10.2 (from scratch)

I did this, and not only it did not solve the problem, but also, now 
I can't boot the 9.1 version, because fsck complains that the file
systems are using features that it doesn't understand.

 - downgrade to 10.0

 - downgrade to 9.3 or 9.1 (but since these are no longer being updated,
   I have to put the server in a private network, close ssh, etc. and
   even then it is somewhat dangerous.)


I also installed another PC with all these versions and I tried to
check which versions have problems. But the tests I did with this
computer were not conclusive. Maybe because it is not the same
hardware (32-bit version) or because I can't duplicate the same load.

 
Thanks in advance for any suggestions

-- 
rps

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