Date: Fri, 10 Jun 2011 13:36:42 +0100 From: Karl Pielorz <kpielorz_lst@tdx.co.uk> To: Jeremy Chadwick <freebsd@jdc.parodius.com> Cc: freebsd-fs@freebsd.org Subject: Re: ZFS scrub 'repaired' pool with no chksum or read errors? Message-ID: <FFB805577AADC590E9BA8089@HexaDeca64.dmpriest.net.uk> In-Reply-To: <20110610093318.GA39276@icarus.home.lan> References: <729A0755FAEF480774EEF4AB@HexaDeca64.dmpriest.net.uk> <20110610093318.GA39276@icarus.home.lan>
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--On 10 June 2011 02:33 -0700 Jeremy Chadwick <freebsd@jdc.parodius.com> wrote: > ZFS experts please correct me, but my experience with this has shown me > that the scrub itself found actual issues while analysing all data on > the entire pool -- more specifically, I believe READ/WRITE/CKSUM are > counters used for when errors are encountered during normal (read: > non-scrub) operations. It's been a while since I've seen this happen, > but have seen it on our Solaris 10 machines at my workplace. I've never > been sure what it means; possibly signs of "bit rot"? I'm reasonably sure (and all the documentation I've seen) seems to indicate that the checksum/read error columns reflect errors found during either normal operations - or scrubs... I've run ZFS on some pretty ropey systems during testing, and it certainly seemed to 'tick up' the errors during scrubs. > If you're worried about your disk (ada0), please provide output from > "smartctl -a /dev/ada0" and I'll be more than happy to review the output > and provide you with any insights. I do believe you when you say it > looks fine, but every model of disk is different in some regard. I'm not overly worried about the disk or the errors - more curious as to why they showed without ticking up anything in the error columns - unless it's not meant to. I can email you the smart output, but there's no pending reallocations, all the SMART parameters are well above their thresholds - additionally smartd hasn't noticed anything 'changing' on the drive to alert about - the drive itself is also reasonably 'new' (and there's no evidence of anything being thrown in syslog/dmesg). If I get time later I might offline the drive and run a long test on it - if that does anything weird & wonderful, I'll take you up on your offer, and email you :-) But like I said, I'm not overly concerned, more curious ;) -Kp
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