On 1 May 2002, babu walad wrote:
After a very quick andefortless install of 8.0 I did a quick check on my hard drives and Suse tells me my Seagate Barraccuda has DMA off while my Maxtor has DMA on.
By "Suse tells me", I'm imaging you mean YaST2. Am I correct in that assumption?
It cautions that turing DMA on may cause loss of data and since I have Suse installed on my Seagate I am cautous about turning it on.
Read the hdparm manual ('man hdparm'), especially the '-X' and '- d' sections. hdparm is the util YaST2 runs to configure DMA. You will read about how dangerous it can be. As the manual states, the problem is not with hdparm (and therefore, not with SuSE), but mostly with buggy chipsets.
I am wondering as to:
1. Why does the Seagate have DMA off and Maxtor on? I did not specify anything special about either of these when I first installed.
Could be the support (or lack there of) of the chipset in the SuSE kernel.
2. What effect other than performance will DMA on have?
Performance is a vague term. DMA doesn't increase performance as much as decrease CPU time, as DMA forces devices to "skip" the CPU. That's why my SoundBlaster sound card, for example, uses DMA.
3. Is it safe to turn it on for Seagate and what is the best way to do so?
If you're not a control freak, tell YaST2 to do it. 99% chance you'll have no problems (how old are the drives, BTW, and what's the motherboard?). If you _are_ a control freak, boot up into single user mode (runlevel 1), and use hdparm to enable/disable DMA and configure the many DMA modes. This is what I do. After I tested many settings, I finally found the "perfect" and stuck it in /etc/init.d/boot.local . Use a combination of the information straight from the hard drive ('hdparm -I /dev/hdX'): it'll exactly tell you what DMA mode your hard drive is in. Post back and tell us whether you succeeded or failed. -- Karol Pietrzak PGP KeyID: 3A1446A0