* Re: raid 5 mismatch_cnt errors [not found] ` <4BF6F3B9.5020405@redhat.com> @ 2010-05-24 9:34 ` Tim Small 2010-05-25 19:09 ` Robert Hancock 0 siblings, 1 reply; 2+ messages in thread From: Tim Small @ 2010-05-24 9:34 UTC (permalink / raw) To: Doug Ledford Cc: MRK, Neil Brown, Trey Scarborough, linux-raid@vger.kernel.org, linux-ide On 21/05/10 21:57, Doug Ledford wrote: > On 05/21/2010 12:40 PM, MRK wrote: > >> On 05/21/2010 04:16 AM, Doug Ledford wrote: >> >> Could the cabling to the drive be causing this? (maybe failing or maybe >> it's partly disconnected) >> I don't remember at what point Linux is at implementing the checksums >> between the controller and the drive. >> > I don't know. I'm not up on the SATA signaling details so I don't know > if it uses CRC on the signal, but I suspect it does and a bad cable > would cause failed requests. But I wouldn't bet my house on it, so I > would ask some SATA gurus. > I wouldn't call myself that, but I believe PATA and SATA-level CRC errors show up in the UDMA_CRC_Error_Count SMART variable - look for a non-zero raw value in the smartctl output. This is presumably just the error-count from the drive's point of view (bad data recd at drive end). I don't know what happens with CRC errors detected at the Linux end - and whether detection is controller-dependant. Better ask on linux-ide. From the SMART attribute name, presumably the earlier PATA transfer modes don't support CRC error detection. An easy thing to check might be to reduce the libata transfer speed from 3GBps to 1.5GBps. Similarly, try to test each drive and SATA port in isolation if you can.... Tim. -- South East Open Source Solutions Limited Registered in England and Wales with company number 06134732. Registered Office: 2 Powell Gardens, Redhill, Surrey, RH1 1TQ VAT number: 900 6633 53 http://seoss.co.uk/ +44-(0)1273-808309 ^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: raid 5 mismatch_cnt errors 2010-05-24 9:34 ` raid 5 mismatch_cnt errors Tim Small @ 2010-05-25 19:09 ` Robert Hancock 0 siblings, 0 replies; 2+ messages in thread From: Robert Hancock @ 2010-05-25 19:09 UTC (permalink / raw) To: Tim Small Cc: Doug Ledford, MRK, Neil Brown, Trey Scarborough, linux-raid@vger.kernel.org, linux-ide On 05/24/2010 03:34 AM, Tim Small wrote: > On 21/05/10 21:57, Doug Ledford wrote: >> On 05/21/2010 12:40 PM, MRK wrote: >>> On 05/21/2010 04:16 AM, Doug Ledford wrote: >>> Could the cabling to the drive be causing this? (maybe failing or maybe >>> it's partly disconnected) >>> I don't remember at what point Linux is at implementing the checksums >>> between the controller and the drive. >> I don't know. I'm not up on the SATA signaling details so I don't know >> if it uses CRC on the signal, but I suspect it does and a bad cable >> would cause failed requests. But I wouldn't bet my house on it, so I >> would ask some SATA gurus. > > I wouldn't call myself that, but I believe PATA and SATA-level CRC > errors show up in the UDMA_CRC_Error_Count SMART variable - look for a > non-zero raw value in the smartctl output. This is presumably just the > error-count from the drive's point of view (bad data recd at drive end). > I don't know what happens with CRC errors detected at the Linux end - > and whether detection is controller-dependant. Better ask on linux-ide. > > > From the SMART attribute name, presumably the earlier PATA transfer > modes don't support CRC error detection. > > An easy thing to check might be to reduce the libata transfer speed from > 3GBps to 1.5GBps. Similarly, try to test each drive and SATA port in > isolation if you can.... ATA transfer errors should cause a bad CRC resulting in a failed transfer which will cause complaints in the kernel log. For PATA, only UDMA modes can detect CRC errors, PIO and MWDMA transfers can't. There are other places where data corruption can occur however, like inside the controller or the drive itself.. ^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2010-05-25 19:09 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
[not found] <4BF56B1F.9080205@locallinux.com>
[not found] ` <20100521071645.497cdcad@notabene.brown>
[not found] ` <4BF5B7D1.3070808@locallinux.com>
[not found] ` <20100521083819.54680dfb@notabene.brown>
[not found] ` <4BF5ECE7.7020907@redhat.com>
[not found] ` <4BF6B782.3060408@shiftmail.org>
[not found] ` <4BF6F3B9.5020405@redhat.com>
2010-05-24 9:34 ` raid 5 mismatch_cnt errors Tim Small
2010-05-25 19:09 ` Robert Hancock
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).