DMA on/off for HD
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. 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. 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. 2. What effect other than performance will DMA on have? 3. Is it safe to turn it on for Seagate and what is the best way to do so? Thanks, Babu __________________________________________________ Do You Yahoo!? Yahoo! Health - your guide to health and wellness http://health.yahoo.com
On Wednesday 01 May 2002 17:55, 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.
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.
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.
2. What effect other than performance will DMA on have?
3. Is it safe to turn it on for Seagate and what is the best way to do so?
Thanks,
Babu
Babu, Are both of these drives on the same channel, same line? Or is one on IDE channel 0 while the other is on channel 1? Do you have ATA100 cable on both (80 strands) or do you have 40 on one & 80 on the other? Are both drives ATA100 or even ATA66 type? If they are on different channels, with all else being equal, then this may be the way SuSE is setup to install them as I noticed my main drive had dma activated (channel 0) and the 2 cd drives did not (channel 1). If all the other requirements are not met, than that may be the cause. If the Seagate is not capable of dma, I don't think SuSE will let you turn it on. Mine didn't let me using hdparm from a shell on my cds. That is the biggest benefit of DMA, the performance gain. DMA=Direct Memory Access Someone correct me if I am mistaken about this, but I believe you can try to turn on DMA to the Seagate without doing harm, your system will just misbehave badly if it is not capable to doing DMA. Patrick -- --- KMail v1.4 --- SuSE Linux Pro v8.0 --- Registered Linux User #225206 Magic Page Products -- Amiga-SuSE-PC Sales & Service URL: http://home.sprintmail.com/~tracerb
--------------------------- Babu, Are both of these drives on the same channel, same line? Or is one on IDE channel 0 while the other is on channel 1? Do you have ATA100 cable on both (80 strands) or do you have 40 on one & 80 on the other? Are both drives ATA100 or even ATA66 type? If they are on different channels, with all else being equal, then this may be the way SuSE is setup to install them as I noticed my main drive had dma activated (channel 0) and the 2 cd drives did not (channel 1). If all the other requirements are not met, than that may be the cause. If the Seagate is not capable of dma, I don't think SuSE will let you turn it on. Mine didn't let me using hdparm from a shell on my cds.
The Seagate drive is setup on a separate IDE channel but it shares it with a CD-ROM (all my IDE buses are used up...). The maxtor is on another IDE channel with another Maxtor drive. All drives on all channels are 40GB, ATA100 drives and the IDE channels are ATA 100. I now suspect it is because I have the CD-ROM on the channel with the Seagate. Does that make sense guys? Thanks!! Babu __________________________________________________ Do You Yahoo!? Yahoo! Health - your guide to health and wellness http://health.yahoo.com
On Thursday 02 May 2002 14:15, babu walad wrote:
The Seagate drive is setup on a separate IDE channel but it shares it with a CD-ROM (all my IDE buses are used up...).
The maxtor is on another IDE channel with another Maxtor drive. All drives on all channels are 40GB, ATA100 drives and the IDE channels are ATA 100.
I now suspect it is because I have the CD-ROM on the channel with the Seagate.
Does that make sense guys?
Thanks!!
Babu
Ok Babu, That helps a lot and I suspect you have hit upon the problem. The Seagate and CDrom are on the same line! IDE behaves badly any time there are two drives on the the same channel, things start to slow down some. Just the nature of the cheap IDE electronics. Be sure also that you have ATA100 cables on the drives too. If you have the old standard 40 strand cables, dma won't be used nor the ata100 only 33mhz for those. You might try switching the Seagate over to the first channel and see how it does then too. Patrick -- --- KMail v1.4 --- SuSE Linux Pro v8.0 --- Registered Linux User #225206 Magic Page Products -- Amiga-SuSE-PC Sales & Service URL: http://home.sprintmail.com/~tracerb
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
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Karol Pietrzak -
Patrick