Date: Mon, 9 Nov 2015 11:08:55 -0800 From: Tim Gustafson <tjg@ucsc.edu> To: freebsd-fs@freebsd.org Subject: ZFS RAID 0+1 Throwing Checksum Errors Message-ID: <CAPyBAS7oYvp6vvzetcGmrXy0_Qn0fXBN_d510w41CguDZCzMxw@mail.gmail.com>
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I have a FreeBSD 10.1 server configured as root-on-zfs with the following pool configuration: NAME STATE READ WRITE CKSUM tank ONLINE 0 0 0 mirror-0 ONLINE 0 0 0 gpt/zfs0 ONLINE 0 0 0 gpt/zfs1 ONLINE 0 0 0 mirror-1 ONLINE 0 0 0 gpt/zfs2 ONLINE 0 0 0 gpt/zfs3 ONLINE 0 0 0 The disks are each 1TB Samsung 850EVO SSDs connected via an mrsas Dell Perc raid controller configured in "RAID Disabled" mode. I run a "zpool scrub" every weekend and every weekend the scrub finds a handful (usually between 1 and 10) checksum errors per disk. The scrub fixes the checksum errors, and I clear the counters and everything seems fine. As far as I know, I do not have any corrupt or missing data. The server is a fairly busy web and database server, handling about 5 million hits per day. I'm wondering if the problem is that the scrub is calculating the checksum for the data on gpt/zfs0, and while that's happening, some data is updated by Apache or MySQL, and then checksum for the data on gpt/zfs1 is calculated, which now doesn't match, and therefore the scrub is reporting an error. Is that possible? If that's not it, could this be a bug? Or should I be worried about my SSDs? What additional data would be helpful for me to share to diagnose this? -- Tim Gustafson Technical Lead, Baskin School of Engineering tjg@ucsc.edu 831-459-5354 Baskin Engineering, Room 313A
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