[9fans] Re: CD install fails, floppy install OK

[koishi@gein.vistech.net]

Status update:
I tried installing with booting from the floppy, but trying to use
the CD as the source to copy the distribution from, got similar
diskWriteRaw errors.

But finally, I found a fix. Thanks to vt3 for the hint!
If I do:
  echo 'dma off' >/dev/sdC0/ctl #The harddisk
*or*:
  echo 'dma off' >/dev/sdD0/ctl #The CD
or both, the installation is successful. If I disable DMA on the HD, I get
this warning at about every 2 seconds in the "copydist" stage:
  entire cache is busy, 1498 dirty -- waking flush thread
  cache is okay again
but this seems harmless.

Another thing I noticed is that after booting the CD, this is printed:
  init: starting /bin/rc
  echo: write error: bad process or channel control request
but everything continues OK.

It seems only either the HD or the CD can have DMA on, not both.
The reason this problem never showed up before for me seems to be the
FreeBSD sysctl hw.ata.atapi_dma which defaults to 0, so bsd didn't try
to use DMA for the CD drive. atacontrol(8) thinks the drives support DMA.
The HD is "QUANTUM FIREBALLP AS20.5/A1Y.1500",
the CD is "HL-DT-ST GCE-8480B/1.03" and it may be useful to print a warning
or switch off dma for the cd if these two drives are detected.

Thanks
--
Varga Peter