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SubjectRe: NFS Data CORRUPTION Between Linux and SunOS 5.5.1
Ben McCann wrote:

> 1. The corruption always begins on a 4096 byte aligned offset
> in the file (i.e. on a page boundary).
>
> 2. 1, 2, or 3 bytes of ZERO are written at the beginning of the page
> and the rest of the page is SHIFTED by that amount. (When we first
> saw this we thought a SCSI controller was failing on the Sun
> server but we've not had any problems with data written via
> NFS to this Sun from a bunch of WinNT boxes we have here. And,
> as I said earlier, 2.1.84 works fine).

When you find the corruption in a particular page, is the following page also
corrupted by having the data shifted over? Or are the extra bytes at the
beginning of the page dropped from the end?

> 3. The location of the smashed page or pages is random. The first
> is usually 4 or 5 megabytes into the file (which is 11M long) but
> occasionally it is only 56K into the file.
>
> 4. The number of corrupted blocks in a 11M file is small, like
> 5 or 10.
>
> Hope this provides a clue. I couldn't fathom why the data was
> SHIFTED because that implies the page was COPIED someplace.
> How many places in the NFS logic COPY entire pages? Perhaps that
> is a place to look.

When you say that the corruption is random, does this mean that sometimes the
file is written correctly? It would be very helpful if you could capture
(e.g. tcpdump) two sessions writing the file, one with the corruption and one
when it's correct.

> Now, a few questions:
>
> 1. How do I vary the NFS block size? (Larry asked that I try that).

The wsize is a mount option to NFS.

> 2. How can I tell if I am using UDP versus TCP? I've done NOTHING
> to explicitly configure NFS. We just use RedHat 5.0 out of the box
> with the 2.1.X kernels.

> 3. Given I can determine UDP vs. TCP, how do I change it to the
> other? Can I assume SunOS 5.5 supports both?

Out of the box Redhat should be UDP, so this isn't a factor. I only mentioned
the possibility because there are still some problems with NFS over TCP in
the current kernels.

Regards,
Bill



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