From owner-freebsd-fs@freebsd.org Mon Nov 9 19:08:58 2015 Return-Path: Delivered-To: freebsd-fs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 9B4A4A2A35A for ; Mon, 9 Nov 2015 19:08:58 +0000 (UTC) (envelope-from tjg@ucsc.edu) Received: from mail-lb0-x231.google.com (mail-lb0-x231.google.com [IPv6:2a00:1450:4010:c04::231]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 3E0161FA3 for ; Mon, 9 Nov 2015 19:08:58 +0000 (UTC) (envelope-from tjg@ucsc.edu) Received: by lbblt2 with SMTP id lt2so86985315lbb.3 for ; Mon, 09 Nov 2015 11:08:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ucsc.edu; s=ucsc-google; h=mime-version:date:message-id:subject:from:to:content-type; bh=w9sQGhrCuDWbYhhxoiDhbQ+7H0/YcqLiVrAGqwZ73lo=; b=WY+GFqLxYirrR1aACKV8LxJMAH5syIS6x6q1QVRsk6jlMsPyHIYBBS15R1DQCcq6aI 87P7r8EKSIQ71V7YQQyAJCngn2Dtn6IPikEXmIl7YA1vE7k75IsJzLODiNItQwrap+F2 QMcaMElzTTtTfHyuVUjmZ4D/IwuvTBR+JEkPI= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:date:message-id:subject:from:to :content-type; bh=w9sQGhrCuDWbYhhxoiDhbQ+7H0/YcqLiVrAGqwZ73lo=; b=kZ4uOxsWD5WfHYA/FPLl55RvXPcOTJL8qliMmnR1cIGpdFgYHPm0umgVHXHO0rB7KM MaaqmTTiqubSWbznTtg+aASjQtAUZbywGECkpaa4JJfgKCDXwbSAjfJEAsV+3i2FVBw7 1uifKLnffhRc75lpnpAe/7WvfKDkwmJ69bVxX20VI1EetU0S3Bn95/JxGItvpZz0+9mm 0mAHpbGNjelsL5jyfjH+wnVoWBKuDtLpU0jyYxEYLqj6AGkQXta5GEYdSjOzvog4oovU 0AqLrxqbdqoVgQXokX/n0Dqfyw/l/VAQmugo6vd1hzgB1DO9Jk9N5/Y9dBUfyO34Pw4T idDA== X-Gm-Message-State: ALoCoQlb/A0NBT47p5uD4KOxK1bCVqZl7ac2d81SBIK7nofhErK4UWBOIxoIutJM4uncEr9PLs2R MIME-Version: 1.0 X-Received: by 10.112.156.2 with SMTP id wa2mr14909100lbb.39.1447096135537; Mon, 09 Nov 2015 11:08:55 -0800 (PST) Received: by 10.25.205.16 with HTTP; Mon, 9 Nov 2015 11:08:55 -0800 (PST) Date: Mon, 9 Nov 2015 11:08:55 -0800 Message-ID: Subject: ZFS RAID 0+1 Throwing Checksum Errors From: Tim Gustafson To: freebsd-fs@freebsd.org Content-Type: text/plain; charset=UTF-8 X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 09 Nov 2015 19:08:58 -0000 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