Patch RFC: Promise SATA300 TX4 hardware bug workaround.

[Alexander Sabourenkov]

Arno J. Klaassen wrote:
> definitely an improvement, but not sufficient (for my setup ) :
> 
> amd64-releng_6 on an ASUS A8V UP (box ran rock-stable
> for years i386-releng_5 with same hardware apart TX4 and
> drives)
> 
> from dmesg :
> 

Setup is identical to mine, except for the drives.
http://lxnt.info/tx4/freebsd/dmesg.text

> 
> Improvement : I now can fsck /dev/concat/data without
> ad6 being detached

It was that bad? wow.

> Persistent problem : when I rsync an nfs-mounted disk to /dev/concat/data,
> I get after about some Gigs of data have been transfered :
> 

That's strange. Are you sure cables, PSU and line power are ok?
Back in October upgrading PSU halved the error count for me (under linux).

> 
> I will test again with "#define PDC_MAXLASTSGSIZE 32*4" (just to see
> if that makes a difference)
> 

Please do.

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./lxnt