Le 2 sept. 09 à 15:27, Frank Middleton a écrit :
On 09/02/09 05:40 AM, Henrik Johansson wrote:For those of us which have already upgraded and written data to our raidz pools, are there any risks of inconsistency, wrong checksums in the pool? Is there a bug id?This may not be a new problem insofar as it may also affect mirrors. As part of the ancient "mirrored drives should not have checksum errors thread", I used Richard Elling's amazing zcksummon script http://www.richardelling.com/Home/scripts-and-programs-1/zcksummon to help diagnose this (thanks, Richard, for all your help). The bottom line is that hardware glitches (as found on cheap PCs without ECC on buses and memory) can put ZFS into a mode where it detects bogus checksum errors. If you set copies=2, it seems to always be able to repair them, but they are never actually repaired.Every time you scrub, it finds a checksum error on the affected file(s)and it pretends to repair it (or may fail if you have copies=1 set). Note: I have not tried this on raidz, only mirrors, where it is highly reproducible. It would be really interesting to see if raidz gets results similar to the mirror case when running zcksummon. Note I have NEVER had this problem on SPARC, only on certain bargain-basement PCs (used as X-Terminals) which as it turns out have mobos notorious for not detecting bus parity errors. If this is the same problem, you can certainly mitigate it by setting copies=2 and actually copying the files (e.g., by promoting a snapshot, which I believe will do this - can someone confirm?). My guess is that snv121 has done something to make the problem more likely to occur, but the problem itself is quite old (predates snv100). Could you share with us some details of your hardware, especially how much memory and if it has ECC orbus parity?
I see the same problem on a workstation with ECC RAM and disks in mirror.
The host is a Dell T5500 with 2 cpus and 24 GB of RAM. Gaëtan -- Gaëtan Lehmann Biologie du Développement et de la Reproduction INRA de Jouy-en-Josas (France) tel: +33 1 34 65 29 66 fax: 01 34 65 29 09 http://voxel.jouy.inra.fr http://www.itk.org http://www.mandriva.org http://www.bepo.fr
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