Re: Blockbusting news, results get worse

From: Pavel Machek (pavel_at_ucw.cz)
Date: 10/29/03

  • Next message: Kristofer T. Karas: "Re: RadeonFB [Re: 2.4.23pre8 - ACPI Kernel Panic on boot]" 
    Date:	Wed, 29 Oct 2003 21:01:41 +0100
To: John Bradford <john@grabjohn.com>

    Hi!

    > > >> or put it under heavy write workload and remove
    > > >> power.
    > > >>
    > > > Can you tell us more about what really happens to disk drives when the
    > > > power is cut while a block is being written? We engage in a lot of
    > > > uninformed speculation, and it would be nice if someone who really knows
    > > > told us....
    > > >
    > > > Do drives have enough capacitance under normal conditions to finish
    > > > writing the block? Does ECC on the drive detect that the block was bad
    > > > and so we don't need to detect it in the FS?
    > >
    > >
    > > Does it really matter to speculate about this?
    > >
    > > If you don't FLUSH CACHE, you have no guarantees your data is on the
    > > platter.
    >
    > I think that the idea that is floating around is to deliberately ruin
    > the formatting on part of the drive in order to simulate a bad block.
    >
    > Operation of disk drives immediately after a power failiure has been
    > discussed before, by the way:
    >
    > http://marc.theaimsgroup.com/?l=linux-kernel&m=100665153518652&w=2

    Well, that looks like pure speculation.

    BTW I *do* believe that powerfail can make the sector bad. Imagine you
    bump into bad sector during write, and need to reallocate...

                                                                    Pavel 

    -- 
When do you have a heart between your knees?
[Johanka's followup: and *two* hearts?]
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