Difference between copy to and copy from nfs mounted disk



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Re: Difference between copy to and copy from nfs mounted disk

Postby rmacklem » Sat, 28 May 2005 10:14:16 GMT

A couple of things you can try:
1 - do "netstat -s" on the server machine and look at the line
  "fragments dropped after timeout, in the Ip: section.
If those are happening, you need to reduce your wsize. (either
the server net interface or some intermediate router/switch is
dropping IP fragments when several are sent to the server, back
to back)
- alternately, try doing mounts over tcp. Those should work ok
   on Linux 2.6 kernels, I think?

You could also try a different net interface or look for a
different driver for the one you have or drop the net interface's
data rate down.

In general, I'd guess the client is transmitting too fast and
writes are getting dropped/retried. (You can also play with the
timeout value, but I recall the mount arg is only in the resolution
of seconds on a Linux mount.)

Good luck with it, rick
ps: Writing is usually slower, but not 200 X as slow.

Re: Difference between copy to and copy from nfs mounted disk

Postby Zlatko Rek » Sat, 28 May 2005 14:30:28 GMT

Rick, thank you for your help. I will try your suggestions.


Re: Difference between copy to and copy from nfs mounted disk

Postby Stuart Friedberg » Sun, 29 May 2005 12:08:16 GMT

Try REMOVING the "no attribute caching" (noac) option and see if that
makes an improvement.

Stu Friedberg

Re: Difference between copy to and copy from nfs mounted disk

Postby Zlatko Rek » Tue, 31 May 2005 14:49:28 GMT

Thank you very much Stuart. You are right, the noacc option is the cause
for slow response. The read time for 100 MB file is 1.2 second now and 
write time is 3.3 seconds.

Best regards.


Similar Threads:

1.Difference between copy to and copy from nfs mounted disk

We have two identical Linux machines (Dual Xeon, Red Hat 8.0, custom 
kernel 2.6.9), connected with 1Gb Ethernet and with cross mounted disk 

I've found that time to copy 100MB file TO nfs mounted disk is appr.
200 times slower than copy FROM nfs mounted disk!

For example: 
Copy over nfs from remote machine vortex3 to local machine vortex2 
(cp /home3/file .) takes 1.5 s, while copy from local machine vortex2 
to remote machine vortex3 (cp file /home3/) takes 305.8 s.

Is this normal or is something wrong with our configuration?

The following lines are from /etc/fstab:

  /dev/hda3      /home2 ext3 defaults                              0 0
  vortex3:/home3 /home3 nfs  rsize=8192,wsize=8192,noac,nfsvers=3  0 0

  /dev/hda3      /home3 ext3 defaults                              0 0
  vortex2:/home2 /home2 nfs  rsize=8192,wsize=8192,noac,nfsvers=3  0 0

Any help is appreciated.


2.HELP: NFS mount hangs when attempting to copy file

I'm having a bit of a problem doing simple copies over an NFS mount.
The client is running Linux (2.6.11), and the server is running Solaris

When I first boot the client, getting NFS directory listings works just
fine.  But the instant I try to copy a file (to or from), the NFS mount
hangs.  While I can still do other network activity (even rlogin to the
server), any NFS access I try to do after that point hangs, including
directory listings.

I have had this same client and server working flawlessly for years.
The only change is that the client is now on a VPN.  However, I have a
Sun machine on the same VPN network segment, and it can copy files with
no problem, so it's not the router that's blocking anything.

Also, after it hangs like that, I cannot reboot the machine normally.
When attempting to unmount the network filesystems, the shutdown hangs,
and I have to hard-reset the machine.

Is there anyone who could please help me to debug this problem?  I
don't even know how to watch to see if there's any network traffic.  As
far as I know, I have NFS setup properly, but I don't know enough about
it to know what options I might try.  I don't even care if the fix
degrades performance; I just want it to not hang.

Does anyone have any ideas?

Thanks very much in advance!

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