NFS io errors on transfer from system running 2.4 to system running 2.5

[Michael Frank]

Speaking of weird errors:

For the last few months I encounter this:

When doing rsync or cp _from_ system running 2.4 _to_ system running 2.5 
get Input/output error errors with random files.

- 2-5 > 2.4 is OK!
- SRebootting, swapping kernel causes the error on the system running 2.4    
- Fast machine > slow machine or slow machine > fast machine
  is no different
- Both systems run same distribution 
- Encountered since 2.4.20 with about 2.5.64 (my first 2.5 kernel)

Example:

/temp contains a couple of crap files

system mhfl2 is running 2.5.6x to 2.5.70-mm3 mounted on
/mnt/mhfl2.

On system running 2.4.20 or 2.4.21-x:
  while ((1)); do cp -f /temp/* /mnt/mhfl2/temp; done

cp: cannot create regular file `/mnt/mhfl2/temp/blah: Input/output error
cp: writing `/mnt/mhfl2/temp/blah: Input/output error

Errors are random, so the files change every run, sometimes there are no errors,
sometimes thre are 3 errors

Q? Any (in)compatibility reason or should I investigate further?

Regards
Michael Frank