Random thoughts of a Geek

As I said in my previous post after setting up XenServer I had problems with horrible perfomance using an IDE drive.  After investigating I found it was because the OS was using a generic ide driver.  Because of this you could not turn DMA/UDMA on for the drive which resulted in pathetic read/write times.



/dev/hdd:
multcount    = 16 (on)
IO_support   =  0 (default 16-bit)
unmaskirq    =  0 (off)
using_dma    =  0 (off)
keepsettings =  0 (off)
readonly     =  0 (off)
readahead    = 256 (on)
geometry     = 19457/255/63, sectors = 312581808, start = 0

I found an article related to previous versions of XenServer that detailed how to modify the boot loader to get a workaround for the problem.  However, it appears in XenServer 5 the  was changed and I was unable to get this to work in the updated location. For those who are looking it is under /boot/ and the conf file is extlinux.conf.

After trying a lot of different things I finally had to rebuild the initrd image file that is used in the boot loader to include the specific driver for my controller.  In my case this was an ATI controller.

Once I did that I could then enable DMA and performance was not an issue after that.