On Sat, 2006-03-25 at 13:43 +1030, Tim wrote: > On Fri, 2006-03-24 at 07:28 +0000, Paul Howarth wrote: > > Was the nodma option used because of mediacheck issues? Turning off > > dma like that will kill hard disk performance as well as CD > > performance. > > I am curious as to why DMA might foul up mediacheck or installations, > but be okay once you have an installed system? I also wonder if, given > the long time involved, it'd be better to first do a mediacheck, then > reboot with DMA for the installation? The kernel code for detecting the end of the data on an IDE CD doesn't work reliably when DMA is on. This leads to false failures in mediacheck when it includes padding data from past the end of the data on the CD in the checksum. Turning off DMA prevents this from happening, so the mediacheck passes. I usually do NFS installs myself, so I never have to burn the downloaded ISO to removable media and don't encounter this issue. It's also faster than installing from CD/DVD. Of course, if you've only one machine you don't have this option. Your suggestion of first doing a mediacheck, then reboot with DMA for the installation is a sane one. Paul.
