Messages in this thread | | | Date | Wed, 28 Nov 2001 18:22:59 +0100 | From | David Balazic <> | Subject | Re: Journaling pointless with today's hard disks? |
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Chris Wedgwood (cw@f00f.org) wrote :
> On Sat, Nov 24, 2001 at 02:03:11PM +0100, Florian Weimer wrote: > > When the drive is powered down during a write operation, the > sector which was being written has got an incorrect checksum > stored on disk. So far, so good---but if the sector is read > later, the drive returns a *permanent*, *hard* error, which can > only be removed by a low-level format (IBM provides a tool for > it). The drive does not automatically map out such sectors. > > AVOID SUCH DRIVES... I have both Seagate and IBM SCSI drives which a > are hot-swappable in a test machine that I used for testing various > journalling filesystems a while back for reliability. > > Some (many) of those tests involved removed the disk during writes > (literally) and checking the results afterwards.
What do you mean by "removed the disk" ?
- rm /dev/hda ? :-) - disconnect the disk from the SCSI or ATA bus ? - from the power supply ? - both ? - something else ?
> > The drives were set not to write-cache (they don't by default, but all > my IDE drives do, so maybe this is a SCSI thing?) > > At no point did I ever see a partial write or corrupted sector; nor > have I seen any appear in the grown table, so as best as I can tell > even under removal with sustain writes there are SOME DRIVES WHERE > THIS ISN'T A PROBLEM. > > Now, since EMC, NetApp, Sun, HP, Compaq, etc. all have products which > presumable depend on this behavior, I don't think it's going to go > away, it perhaps will just become important to know which drives are > brain-damaged and list them so people can avoid them. > > As this will affect the Windows world too consumer pressure will > hopefully rectify this problem. > > --cw > > P.S. Write-caching in hard-drives is insanely dangerous for > journalling filesystems and can result in all sorts of nasties. > I recommend people turn this off in their init scripts (perhaps I > will send a patch for the kernel to do this on boot, I just > wonder if it will eat some drives).
-- David Balazic -------------- "Be excellent to each other." - Bill S. Preston, Esq., & "Ted" Theodore Logan - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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