topic Re: enable DMA in Operating System - Linux

enable DMA

peterchu — Mon, 09 Feb 2004 01:47:01 GMT

I an installing a dell application to my linux server , it pop up the below message , how can I enable the DMA ? thx

Turning off DMA on IDE CDROM drives.
Disabling DMA for CDROM /dev/hda
Message: [Start] -> Please wait
error : please accept user agreement license, see Server Administrator's user's
guide for help

Re: enable DMA

Mark Grant — Mon, 09 Feb 2004 01:56:39 GMT

You enable dma with "hdparm -d1 " However, I'm not sure you want to turn it on for these CDROMS. Whichever application you are installing seems to want to turn it off. Probably for a good reason. There have been issues with contention between hard disk and CDROMS with DMA enabled. On the other hand, you can try turning it on and see if you get a performance loss/increase anywhere.

Re: enable DMA

Ragu_1 — Mon, 09 Feb 2004 12:26:13 GMT

I think you need not bother about the DMA settings for your CDROM drives. Be careful when you test out hdparm on your IDE hard disk drives, if at all. If you use hdparm carefully, you can get definite increase in speeds, in the range 4-6 % . Be warned!!

Re: enable DMA

K.C. Chan — Mon, 09 Feb 2004 16:37:48 GMT

You may need to turn this option on in your kernel if it is not. Usually by default, it compile with this option. You will find out if this option is turn on or when when you issue hdparm -d1 command on your target drive/cdrom.

Re: enable DMA

Matthew Couper — Tue, 10 Feb 2004 11:59:25 GMT

Depends on what distro you are using
Most will allow DMA to be enabled on CDROMs with "hdparm -d1 /dev/device" but Red Hat has this completely disabled by default

From the RH8 release notes (this was not in the RH9 notes for some reason...)

DMA is disabled on CD-ROM drives in this release in a different but more reliable way than previously. If you are sure that your CD-ROM drive is capable of IDE DMA, place the following line in the /etc/modules.conf file:

options ide-cd dma=1