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    SubjectRe: 2.5.46: ide-cd cdrecord success report
    On Thu, Nov 07, 2002 at 08:14:09PM +0200, MdkDev wrote:
    >
    > > Thanks, this is good information. Was the destination for the 'dd' and
    > > the source CD image on the same drive? What filesystem were you using?
    >
    > Yes, destination for the dd and the source for the CD image was on the
    > same drive. I'm using ext3 filesystem.
    >
    > > I notice you used a 4x writer...I'll try lowering my write speed to 4x
    > > and see if that makes a difference. I'll also see if I can rig up an
    > > IDE disk instead of SCSI.
    >
    > The burner is capable of writing 16x (CDR) or 10x (CDRW) but the speed was
    > 4x in this case because of the media. I'll try and repeat the test using
    > max speed.

    I've done some more testing and narrowed the problem down a little. I
    switched to an IDE drive to rule out SCSI and found that the problem is
    still with me: a parallel `dd` to the image source drive still kills burn.

    Then I lowered the write speed from 12x down to 4x to match yours...and
    then the problem went away. A look at `vmstat 1` shows that the heavy
    write load causes the read throughput to drop to about 768 KB/sec.
    That's far too slow for 12x but is just about right for 4x. Makes sense,
    then that a 4x burn survives.

    It's easy to duplicate without involving cdrecord at all. Just do...

    dd if=/dev/hda1 of=/dev/null bs=1M

    ...in parallel with...

    dd if=/dev/zero of=/mnt/foo bs=1M

    When you kick in the write load, the read throughput drops to < 1
    MB/sec. `vmstat 1` output below shows the transition...

    --Adam

    procs memory swap io system cpu
    r b w swpd free buff cache si so bi bo in cs us sy id
    2 0 0 4272 112684 20356 36856 0 0 0 16 1016 72 5 0 95
    0 1 1 4272 108476 23676 36856 0 0 3320 0 1067 224 13 4 83
    1 0 1 4272 96656 35580 36856 0 0 11904 0 1192 474 30 39 30
    0 1 0 4272 84836 47356 36856 0 0 11776 0 1192 463 30 42 27
    0 1 1 4272 72956 59268 36856 0 0 11904 40 1313 1139 44 38 18
    0 1 0 4272 61076 71044 36856 0 0 11776 0 1200 478 29 43 29
    0 1 0 4272 49256 82828 36856 0 0 11784 0 1199 522 39 37 24
    0 1 0 4272 37196 94732 36856 0 0 11904 0 1199 497 35 38 26
    0 1 0 4272 25256 106508 36856 0 0 11776 0 1199 512 32 43 24
    1 2 3 4692 2468 75604 90132 0 420 9608 10888 1189 721 19 75 6
    0 2 3 4692 3540 46932 117580 0 0 808 10428 1093 287 30 70 0
    0 2 3 4692 3448 42916 121624 0 0 1024 8824 1099 266 65 35 0
    0 2 3 4692 3200 35152 129692 0 0 1024 6512 1088 294 55 45 0
    0 2 4 4692 1564 24640 141696 0 0 768 7688 1091 277 44 56 0
    1 1 2 4692 3492 19044 145484 0 0 1024 5956 1084 285 69 31 0
    0 2 3 4692 3492 12020 152448 0 0 768 7192 1085 298 55 45 0
    0 2 3 4692 3432 12444 152056 0 0 676 6852 1086 266 55 45 0
    0 2 3 4692 3612 12196 152288 0 0 768 5724 1083 287 55 45 0
    0 2 3 4692 3552 12580 151900 0 0 768 7756 1088 272 65 35 0
    2 2 3 4692 3492 12840 152048 0 0 1024 5032 1195 691 66 34 0
    0 2 3 4692 3792 13304 151212 0 0 772 7452 1191 586 60 40 0

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