[OpenAFS] possible microsoft excel 2010 corruption issue on openafs volumes

Jonathan Nilsson jnilsson@uci.edu
Wed, 21 Dec 2011 10:31:24 -0800


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> On 12/21/2011 9:15 AM, Arthur Prokosch wrote:
> > Jonathan, or others who experienced this bug -- have you seen corrupt
> > excel files with modification times from before when a volume was
> > served by 1.6.0?
>

Hmm, I hadn't actually thought of that scenario, or looked for evidence to
support it. The first few cases of corruption were for files modified after
a volume was moved to 1.6 servers.  Since then, all volumes have been moved
back to 1.4 servers and I have not looked as closely at the evidence (just
performing restores based on the modification timestamp).


> In all of the cases I have seen the corruption was triggered by opening
> and closing an excel spreadsheet which results in 8 bytes being written
> to the spreadsheet header.  The header becomes corrupted with either the
> first 1K or 4K of the file being replaced by NULs instead of the actual
> header file.  The last modification timestamp is preserved by Excel.


Ah, that explains it! Thanks for discovering this behavior, Jeffery. Since
I did not know that Excel had the behavior, for each file I tested
restoring many different versions of before finding that I could reliably
restore the one from the latest modification timestamp.

-- 
Jonathan.Nilsson at uci dot edu
Social Sciences Computing Services
SSPB 1265 | 949.824.1536

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<div class=3D"gmail_quote"><br><blockquote class=3D"gmail_quote" style=3D"m=
argin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div>On 12/21=
/2011 9:15 AM, Arthur Prokosch wrote:<br>
&gt; Jonathan, or others who experienced this bug -- have you seen corrupt<=
br>
&gt; excel files with modification times from before when a volume was<br>
&gt; served by 1.6.0?<br></div></blockquote><div><br></div><div>Hmm, I hadn=
&#39;t actually thought of that scenario, or looked for evidence to support=
 it. The first few cases of corruption were for files modified after a volu=
me was moved to 1.6 servers. =A0Since then, all volumes have been moved bac=
k to 1.4 servers and I have not looked as closely at the evidence (just per=
forming restores based on the modification timestamp).</div>


<div>=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;=
border-left:1px #ccc solid;padding-left:1ex"><div>In all of the cases I hav=
e seen the corruption was triggered by opening</div>
and closing an excel spreadsheet which results in 8 bytes being written<br>
to the spreadsheet header. =A0The header becomes corrupted with either the<=
br>
first 1K or 4K of the file being replaced by NULs instead of the actual<br>
header file. =A0The last modification timestamp is preserved by Excel.</blo=
ckquote><div><br></div><div>Ah, that explains it! Thanks for discovering th=
is behavior, Jeffery. Since I did not know that Excel had the behavior, for=
 each file I tested restoring many different versions of before finding tha=
t I could reliably restore the one from the latest modification timestamp.<=
/div>


</div><div><br></div>-- <br><div><font face=3D"&#39;courier new&#39;, monos=
pace">Jonathan.Nilsson at uci dot edu</font></div><div><font face=3D"&#39;c=
ourier new&#39;, monospace">Social Sciences Computing Services</font></div>


<div><span style=3D"font-family:&#39;courier new&#39;,monospace">SSPB 1265 =
| <a href=3D"tel:949.824.1536" value=3D"+19498241536" target=3D"_blank">949=
.824.1536</a></span></div><br>

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