Date: Wed, 08 Feb 2012 20:31:15 +0100 From: Peter Maloney <peter.maloney@brockmann-consult.de> To: freebsd-fs@freebsd.org Subject: Re: zfs checksums on non-raidz Message-ID: <4F32CD83.6000101@brockmann-consult.de> In-Reply-To: <4F32CD14.1030508@brockmann-consult.de> References: <20120208184728.GH6814@zero> <4F32CD14.1030508@brockmann-consult.de>
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ps. Try what I showed you in a vm rather than a real system, to keep your data safe. Am 08.02.2012 20:29, schrieb Peter Maloney: > Am 08.02.2012 19:47, schrieb Tom Vier: >> In mirror and single dev zpools, are data and metadata still checksummed, or >> only when using raidz? >> >> I've only been able to determine so far that the uberblocks at the zpool level >> are always checksummed (according to Sun's on-disk format pdf). >> > Everything, even a single disk, is checksummed. > > Test it with: > > > zpool create testpool gpt/testslice > cp /some/big/test/file /testpool/ > > # next command is dangerous because it means you can now directly write > to disks and damage the data > sysctl kern.geom.debugflags=0x10 > > # next command is more dangerous, because it intentionally destroys data > on the slice (be careful about what you put in of=... ) > dd if=/dev/zero of=/dev/gpt/testslice bs=1M count=5000 > > # after this command, you should have some checksum errors > md5 /testpool/file > > # after this command and waiting, you should have all the errors there > are (all files, including not read by the md5 above) > zpool scrub testpool > > ...wait... > > zpool status testpool > > Now you probably (depending on whether or not the part we wrote with dd > actually went on top of where data was placed) have checksum errors, and > a message about an unrecoverable file. If it was raidz or mirror, it > would have automatically fixed it for you, but with no redundancy, all > the checksum can do is tell you the file is broken. > _______________________________________________ > freebsd-fs@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org"
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