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    SubjectRe: RAID problems
    On Tue, Jul 30, 2002 at 10:46:55PM -0400, Bill Davidsen wrote:
    ...
    > I think you misread my comment, it was not "why doesn't the documentation
    > say this" but rather "why does software RAID have this problem?"

    Ok, my bad.

    - btw. I CC'ed linux-raid as this is getting a little OT for
    linux-kernel. Let's let the thread migrate to linux-raid instead...

    > I know
    > this can happen in theory, but it seems that the docs imply that this
    > isn't a surprise in practice. I've been running systems with SCSI RAID and

    I would say it's not a surprise as such, but it's something that really
    should be a very very rare occurrance.

    I've seen it maybe once on a production system, having run MD on quite a
    few computers for the past half decade. And I've had a few handfulls of
    people asking me about it over the years.

    ...
    > I just surprised that the software RAID doesn't have better luck with
    > this, I don't see any magic other than maybe a bus reset the firmware
    > would be doing, and I'm wondering why this seems to be common with Linux.

    I don't have the impression that it is common on stable hardware. Can
    anyone who runs SW RAID on a number (greater than 1) of machines comment
    on this ?

    However, some people run their RAID-5 arrays on the same SCSI busses as
    their Zip drives, their scanners, and five other el-cheapo almost-scsi
    devices, and that is just *bound* to cause this kind of mess when one of
    the devices decide to lock up the bus.

    You don't see this with HW raid because you don't put your $15
    almost-scsi magic-foo device on your $2k HW RAID controller.

    There might be other simple reasons why some HW cards don't show this
    behaviour - they might simply maintain their superblocks differently
    from Linux SW RAID. I have *no* idea how current controllers do this.

    > Or am I misreading the frequency with which it happens?

    I hope ;)

    At least in the "stable hardware" situation. Comments, please...

    ...
    > Thye words are clear, I'm surprised at the behaviour. Yes, I know that's
    > not your thing.

    I *will* be surprised if it turns out that this is really a common
    occurrence for people. :)

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