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Old 08-16-2006, 04:52 AM   #1
PhillipHuang
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Registered: Aug 2006
Location: Shen Zhen
Distribution: Ubuntu 10.04
Posts: 198

Rep: Reputation: 33
Huge file issue of NFS


Two servers,
One is installed CentOS4.3(2.6.9-34), named "A";
The other is install RedHat7.3(2.4.19) named "B"

In "A", I used 'dd' command to create two huge files(38GB and 19GB) in '/test' directory:
# dd if=/dev/urandom of=/test/hugefile bs=10M count=3800
# dd if=/dev/urandom of=/test/hugefile2 bs=10M count=1900

"B" has a shared directory "shares",then I mount this "shares" to A's "NFS_Test":
# mount xxx.xxx.xxx.xxx:/shares /NFS_test

I wrote the following script to cp and compare files:

#!/bin/bash
# NFStest

#THIS WILL COPY $1 TO $2
#THEN COMPARE WITH DIFF, AND PUT THE RESULTS IN $3

#1ST COPY 1 TO 2
cp -v $1 $2 >> $3
sleep 100

#then compare them using diff
diff -s $1 $2 >> $3

while :
do
#then copy $2 to $1.tmp
cp -v $2 $1.tmp >>$3
sleep 100

#then compare $1 with $1.tmp
diff -s $1 $1.tmp >> $3

#then copy $1.tmp to $2
cp -v $1.tmp $2 >>$3
sleep 100

#then compare using diff
diff -s $1.tmp $2 >>$3

#then compare $1 and $2
diff -s $1 $2 >> $3
done

Here,
$1 is the source. (A: /test/hugefile, hugefile1)
$2 is the destination.(A: /NFS_test)
$3 is the log where everything is pumped into.

At this time. I run the script in two console simultaneously:

# ./NFStest /test/hugefile /NFS_test/hugefile.copy /nfstest.log

# ./NFStest /test/hugefile1 /NFS_test/hugefile1.copy /nfstest1.log

After more than two hours, I read the "nfstest1.log", it showed that hugefile1 and hugefile1.copy are different!

In the early test, I created a 160G file, and run the script in only one console, the result of 'diff' said them are same even this testing was running about a week!

How could this "diff" happen? Please help me.

Thanks and regards,
Phillip
 
Old 08-16-2006, 03:36 PM   #2
pk21
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Registered: Jun 2002
Location: Netherlands - Amsterdam
Distribution: RedHat 9
Posts: 549

Rep: Reputation: 30
Have no idea wat that nfs script is for, but RedHat7.3 is pretty old. It uses a 2.4 kernel and if this kernel doesn't support large files, then there probably is a limit of 2.1Gb. Maybe the 2.1Gb limit is the problem, you will have to check the file sizes on the redhat machine.
 
  


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