Re: data corruption with nvidia chipsets and IDE/SATA drives // memory hole mapping related bug?!

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Christoph Anton Mitterer wrote:
Hi.

Perhaps some of you have read my older two threads:
http://marc.theaimsgroup.com/?t=116312440000001&r=1&w=2 and the even
older http://marc.theaimsgroup.com/?t=116291314500001&r=1&w=2

The issue was basically the following:
I found a severe bug mainly by fortune because it occurs very rarely.
My test looks like the following: I have about 30GB of testing data on
my harddisk,... I repeat verifying sha512 sums on these files and check
if errors occur.
One test pass verifies the 30GB 50 times,... about one to four
differences are found in each pass.

The corrupted data is not one single completely wrong block of data or
so,.. but if you look at the area of the file where differences are
found,.. than some bytes are ok,.. some are wrong,.. and so on (seems to
be randomly).

Also, there seems to be no event that triggers the corruption,.. it
seems to be randomly, too.

It is really definitely not a harware issue (see my old threads my
emails to Tyan/Hitachi and my "workaround" below. My system isn't
overclocked.



My System:
Mainboard: Tyan S2895
Chipsets: Nvidia nforce professional 2200 and 2050 and AMD 8131
CPU: 2x DualCore Opterons model 275
RAM: 4GB Kingston Registered/ECC
Diskdrives: IBM/Hitachi: 1 PATA, 2 SATA


The data corruption error occurs on all drives.


You might have a look at the emails between me and Tyan and Hitachi,..
they contain probalby lots of valuable information (especially my
different tests).



Some days ago,.. an engineer of Tyan suggested me to boot the kernel
with mem=3072M.
When doing this,.. the issue did not occur (I don't want to say it was
solved. Why? See my last emails to Tyan!)
Then he suggested me to disable the memory hole mapping in the BIOS,...
When doing so,.. the error doesn't occur, too.
But I loose about 2GB RAM,.. and,.. more important,.. I cant believe
that this is responsible for the whole issue. I don't consider it a
solution but more a poor workaround which perhaps only by fortune solves
the issue (Why? See my last eMails to Tyan ;) )



So I'd like to ask you if you perhaps could read the current information
in this and previous mails,.. and tell me your opinions.
It is very likely that a large number of users suffer from this error
(namely all Nvidia chipset users) but only few (there are some,.. I
found most of them in the Nvidia forums,.. and they have exactly the
same issue) identify this as an error because it's so rare.

Perhaps someone have an idea why disabling the memhole mapping solves
it. I've always thought that memhole mapping just moves some address
space to higher addreses to avoid the conflict between address space for
PCI devices and address space for pyhsical memory.
But this should be just a simple addition and not solve this obviously
complex error.

If this is related to some problem with using the GART IOMMU with memory hole remapping enabled, then 2.6.20-rc kernels may avoid this problem on nForce4 CK804/MCP04 chipsets as far as transfers to/from the SATA controller are concerned as the sata_nv driver now supports 64-bit DMA on these chipsets and so no longer requires the IOMMU.

--
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from [email protected]
Home Page: http://www.roberthancock.com/

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