Date: Wed, 4 Jan 2006 21:30:12 GMT From: =?ISO-8859-1?Q?S=F8ren_Schmidt?= <sos@deepcore.dk> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/85603: [ata] FS corruption and 'uncorrectable' DMA errors on ATA disks after unclean shutdown Message-ID: <200601042130.k04LUCAZ044309@freefall.freebsd.org>
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The following reply was made to PR kern/85603; it has been noted by GNATS. From: =?ISO-8859-1?Q?S=F8ren_Schmidt?= <sos@deepcore.dk> To: bug-followup@FreeBSD.org, philip@FreeBSD.org Cc: Subject: Re: kern/85603: [ata] FS corruption and 'uncorrectable' DMA errors on ATA disks after unclean shutdown Date: Wed, 04 Jan 2006 20:24:17 +0100 Uncorrectable errors can very easily be encountered if there was a write operation on a drive during a power failure. The problem is that the sector(s) isn't completely written and the ECC information isn't updated correctly on the media. This can render from 1 sector to an entire track (seen from the disks perspective not nessesarily the geometry used) due to the way data are stored on modern disks. Now, if the disk still has spare sectors available a write to the bad sectors will be remapped and the disk will seem to be functional again. I have seen at least a dozen modern systems that actually powercycles during reset, which can be a very bad idea if the drives have decided to write out cachebuffers etc during a reboot. -Søren
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