Local Lan Transfers data integrity failure (was: NFS data integrity failure)

Bigbrother bigbrother at bonbon.net
Mon Oct 18 08:02:44 PDT 2004

> -----Original Message-----
> From: Gary Dunn [mailto:knowtree at aloha.com] 
> Subject: Re: NFS data integrity failure
> On Thu, 2004-10-14 at 07:58, Bigbrother wrote:
> > 
> > MachineB mounts machineA:/disk and puts 1.2 GB of data from 
> its disk to the
> > machineA dick.  A CRC check performed on the copied files show that
> > everything is correct. (always!)
> Then do it this way :-)
> Seriously, though, to isolate NFS you need to exercise the network and
> file systems using other methods. How about transfering the same files
> using a) ftp and b) scp. If the problem is dropped packets or
> fragmentation or stuck bits in the NIC, those methods will be equally
> unsuccessful.
> Does either machine ever display an error message about nfs going down
> then coming back? I can't remember the exact words, something like
> connection lost then restored. When this happens to me at 
> work it is due
> to the ethernet switch port one system is connected to coming 
> up in half
> duplex instead of full duplex. Once it was a bad cat5 cable. 
> Are the file sizes different?
> -- 
> Gary Dunn


Thanks Gary for your useful suggestions....Following the analysis of the
problem my results indicate until now:

A) A thorough multi-pass memory test (using memtest86) showed NO memory

--Transfers between machineA and machineB on 1.2 GB of data

B)When I SCP using machineA (get)I always get some CRC errors
C)When I FTP using machineA (get)I always get some CRC errors
D)When I SCP using machineB (get)no CRC errors are produced (target==source)
E)When I FTP using machineB (get) no CRC errors are produced

F)When I FTP (put) using machineB CRC errors are produced
G)When I NFS (put) using machineB CRC errors are NEVER produced
E) When I SCP (put) using machineB CRC errors are produced)

The file sizes are always the same at 15.000.000. 
Even the corrupted files have the same file size.

The SYSLOG does not log anything related to NFS or disc problems. NFS does
not go down
and come back. So it is not NFS only problem.

Also, note that I have optimized my FreeBSD by using these values:
(I do not know if they interfere with my machine)

/sbin/sysctl -w kern.ipc.somaxconn=4096
/sbin/sysctl -w kern.maxfiles=65536
/sbin/sysctl -w kern.maxfilesperproc=10050
/sbin/sysctl -w net.inet.tcp.sendspace=3217968
/sbin/sysctl -w net.inet.tcp.recvspace=3217968
/sbin/sysctl -w kern.ipc.maxsockbuf=8388608
/sbin/sysctl -w net.inet.udp.recvspace=3217968
/sbin/sysctl -w net.inet.raw.recvspace=3217968

What do you think is causing this?

What tests can I do in order to further investigate this problem?

Thanks again people!!!

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