buffer write errors 7.10 
Author Message
 buffer write errors 7.10

We're getting some really strange errors in a UnixWare 2.01 port
of 7.10.UC1 OnLine.  It's been dead-solid reliable for a year, but
we're beginning to get tight on disk space (~16 gig now).  We have
gotten a repeatable error in which loading a table in one database
chunk causes overwrites into another chunk.  The overwrites are in pages
5,6,7, and 8 in the chunks.  It's happening where chunk 10 is
corrupted by chunk 25 data and where chunk 14 is corrupted by
chunk 27 data.

It looks exactly like I have overlapping chunks...that's the first thing
I checked.  Informix Support called in and is really confused.  They verified
that there is **no** overlap.  They also used tbpatch to write to one
of the confused chunks.  The change does not appear in the other half
of the confused pair, indicating that there is really no overlap.  The
symptoms are that a table gets totally blown away when the cross-writes
occur.  Informix says it is not an Informix problem and are pointing
to possible controller problems (but a _repeatable_ error ???).

I'm pursuing the possible controller problem, but I'd like to see if
anyone else has seen anything remotely resembling this, in **any**
version of 7.XX on **any** platform.  I'd like to be able to point to
some bug reports if anyone else has seen anything like this.

Thanks
Joe

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Wed, 18 Jun 1902 08:00:00 GMT
 buffer write errors 7.10

Several years ago I had a similar problem using C-ISAM under SCO UNIX
and it turned out to be the 386 mother board. I discovered this after
replacing everything else first.  There was a small burn mark on the
edge of the mother board which, by the way, passed diagnostics.

Quote:

>We're getting some really strange errors in a UnixWare 2.01 port
>of 7.10.UC1 OnLine.  It's been dead-solid reliable for a year, but
>we're beginning to get tight on disk space (~16 gig now).  

<snip>


Wed, 18 Jun 1902 08:00:00 GMT
 buffer write errors 7.10

: It looks exactly like I have overlapping chunks...that's the first thing
: I checked.  Informix Support called in and is really confused.  They verified
: that there is **no** overlap.  They also used tbpatch to write to one

Responding to my own posting:

We solved the problem, and the process may be of help to others.  We **DID**
have overlapping chunks, but it was at the OS, not at the Informix level.  

When the disk was originally set up by the vendor (creating all of the
disk devices with their major and minor device numbers), there was a typo
on one of the starting tracks for a partition.  Rather than starting
at 802000 as the real partition should have, it started at 028000.  This
caused an overlap that overlapped three partitions on each disk.  One of
the overlaps was on these chunks that were giving me problems.  The other
overlap was at the very end of rootdbs and at the end of one of my temp
spaces. We never used the back end of rootdbs or the tempdbs, so it never
hit us.  We were all looking at the chunk layout (offsets and lengths) in
Informix and at the major and minor device numbers to make sure we weren't
messing up and pointing two chunks to the same device.  All that was OK.
Only when we printed up a VTOC (volume table of contents) of the actual
disks themselves did we find the real problem.

FYI
Joe

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Wed, 18 Jun 1902 08:00:00 GMT
 buffer write errors 7.10


Quote:
> We're getting some really strange errors in a UnixWare 2.01 port
> of 7.10.UC1 OnLine.  It's been dead-solid reliable for a year, but

snip..

What size of offset are you using into each chunk?  



Wed, 18 Jun 1902 08:00:00 GMT
 
 [ 4 post ] 

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