You will find that the limit of the disk access is not whether you are
using udma66 or udma33 or scsi but the maximum data rate on for the disk
drive. The typical max sustained data rate on an ibm deskstar(ide) 34GXP
is between 14 and 23 MB/sec and for an ultrastar 36LZX scsi drive the
max sustained data rate is between 22 and 36 MB/sec (I looked on maxtors
site, but the location of the drive specs was not very evident besides
over that past year with all the disk drive problems that I have read
and helped with, I don't use anything but ibm drives now). Neither the
ide nor the scsi drive can exceed the bus speed and often even two or
more drives do not have the capacity to exceed the host interface data
rate capability. If you go look at the max sustained data rate for your
drive, if you can find it on maxtor's website, you will be delighted to
discover that you have deluded yourself (this is not an insult but a
reality check so stuff the flames somewhere else; you have also had a
little bit of help from some marketing weenies) about the speed of your
system and that the udma33 will likely deliver the same overall
performance. And until the udma66 drivers are completely debugged for
linux, you will have a lot more reliable system if you stick with the
udma33 interface for now.
Also, the last time I that I looked at the udma66 driver a couple of
months ago, I read that if you use use hdparm with the udma66 driver
then you are asking for problems since the driver already optimizes the
interface and that hdparm will screw it up. I just do not remember the
exact details of what the author mentioned about his driver, only that
hdparm is a no-no with the udma66 linux driver.
Tom Berkley
Yann Le Du wrote:
>
> Hello,
>
> I have a Supermicro PIIIDME with dual Pentium 800E Processors inside, two
> ide Maxtor DiamonMax Plus 40.9 Gb (Primary master and secondary
> master) and one Quantum Atlas 10K on a Adaptec 2960 160Mb/s (64 bits).
>
> My root and boot are on hda, and the rest is on sda (with /tmp and
> /var/log on hda too). The fs I use is reiser-fs, except for /boot which is
> ext2 (as said necessary in the manual).
>
> I run SUSE 6.4 (kernel 2.2.14 with SMP). My two processors are listed, and
> I can make SMP on them. But...
>
> The problem is that if I set the dma on the ide hard disks using
>
> hdparm -d1 /dev/hda
>
> and then copy a large size pack of files (say 700Mb) between the sda and
> the hda, then I have "Segmentation faults" during the copy, or even
> worse the "cp" command is listed in the processes but nothing works (no
> disk activity, and the cp command takes 0% cpu) and I cannot kill the
> process. And then sometimes the system halts (I have to reset the computer
> manually).
>
> If I remove the udma setting, everything works fine.
>
> The problem is that without udma, my Maxtor drives are pretty slow.
>
> What can I do ? Buy a bunch of SCSI ?
>
> Thanks,
>
> Yann Le Du
>
> ------------------------------------------------------------------------
> Yann Le Du E-mail: [EMAIL PROTECTED]
> Theoretical Physics Web : http://cdfinfo.in2p3.fr/~ledu/
> 1, Keble Road
> University of Oxford
> Oxford, OX1 3NP Phone : (44) (0)1865 273 989
> United Kingdom Fax : (44) (0)1865 273 947
> ------------------------------------------------------------------------
>
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