From owner-freebsd-fs@freebsd.org Sun Sep 4 18:11:40 2016 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 C08CCB71F4D for ; Sun, 4 Sep 2016 18:11:40 +0000 (UTC) (envelope-from paul@kraus-haus.org) Received: from mail-qk0-x234.google.com (mail-qk0-x234.google.com [IPv6:2607:f8b0:400d:c09::234]) (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 7EB6683F for ; Sun, 4 Sep 2016 18:11:40 +0000 (UTC) (envelope-from paul@kraus-haus.org) Received: by mail-qk0-x234.google.com with SMTP id z190so173628635qkc.0 for ; Sun, 04 Sep 2016 11:11:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kraus-haus-org.20150623.gappssmtp.com; s=20150623; h=mime-version:subject:from:in-reply-to:date :content-transfer-encoding:message-id:references:to; bh=IAIfkPXT99wrPrIrRDamVK4ZMTI0oFGl6cXiC8ksxOg=; b=ELV4ybHudF0nEpAMi6g4Uc4DjkOy17fNoNzdm4Jglfa73RElhEXOcqjybol/RG5PNq paBUfv8m4Vorzd7+rwI9P/UeLVNWreBh+ZAH0pb/IptKi3OXBlrrH0gKlaOurUySP0yT vcAVqDP4LJA8nsXSAzZcGAsjUw35ccXzt3GjNNLWJfTyHS6uhSsZb+ygMRN9ajVh7HSl Az+C+q0CC3HdUKXwWV04nHXRNnmFiMkdJllh1u8VtIyGAUHoLNzFgVDT/NdKJHaH0scK +DRD/T4OFsc5Ma6LE1c+SmrrbBSm774TtCdThlORcUqediFEdnLXZtmtQajPOKEg/eEH FP+Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date :content-transfer-encoding:message-id:references:to; bh=IAIfkPXT99wrPrIrRDamVK4ZMTI0oFGl6cXiC8ksxOg=; b=TyDcvSNOF3fQQoV+5/KOSZRL8NrgWUaqEqdTsj1QA6cASvHoe9OIRl+pQw6KEkcP/j DhDQojmEVO/p+agG91ib2BByM9H2GUmg/duZS1YO8gFowBz7PwxnSAXBlaSpUnUvgyOc GDV8nRp1n6tWT1cLuSRUo0kRnk8/CXhieq5e/IhAg8n/sytVzYYwirYTbwXJBFqC/jFd HwjEPRRlQHCIAnLRNcyLMcgIlS8s+4ZCy5d8Hc1mMP2DFjFD6aZ2mQDb/ETCDRLfbAct qEXbE/Lv1Wc47RGr9pgFx/lh7s6R/m+qv3DZFn6WXRB7qnjksUASM4/A2HrT6ef441sI 6OGg== X-Gm-Message-State: AE9vXwNvoZKtdpn6VdYOwrjJvM0YfdDttAvZcuDnF1abnL2aqBtGPi5IyuqYLw7o45n3tw== X-Received: by 10.55.156.129 with SMTP id f123mr11869063qke.148.1473012699552; Sun, 04 Sep 2016 11:11:39 -0700 (PDT) Received: from [192.168.2.133] (pool-100-4-209-221.albyny.fios.verizon.net. [100.4.209.221]) by smtp.gmail.com with ESMTPSA id l187sm12495081qkc.8.2016.09.04.11.11.38 (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Sun, 04 Sep 2016 11:11:38 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Subject: Re: phantom snapshots From: Paul Kraus In-Reply-To: Date: Sun, 4 Sep 2016 14:11:37 -0400 Content-Transfer-Encoding: quoted-printable Message-Id: <8B542627-1FBA-469D-BAAE-60C9BB615326@kraus-haus.org> References: <58816ff0-3ab2-cbae-3d50-c4d5e89d9773@kateley.com> <57C9D1FB.6040904@b1t.name> To: FreeBSD FS X-Mailer: Apple Mail (2.3124) X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 04 Sep 2016 18:11:40 -0000 > On Sep 2, 2016, at 3:41 PM, Linda Kateley = wrote: >=20 > How did you remove the files in the snapshot? I keep trying but it is = read-only? Can I remount it read-write? Snapshots are by design read only copies of the data. When you create a ZFS snapshot you are (functionally) copying the = Uberblock for the dataset and preventing any slabs used by it from being = added to the free list. This is partly why ZFS snapshots have little to = no performance penalty. When you clone a snapshot you are effectively making a read-write copy = of it. So to delete files from a snapshot you destroy the snapshot itself. If = the snapshot has already been destroyed, then you _may_ be running into = the delayed snapshot destruction implemented a bunch of years ago for = some really good reasons. If a system rebooted in the midst of a = snapshot destruction, the reboot would not complete until the snapshot = destruction was completely done. For large snapshots this could be hours = (or even days). So the zfs destroy command returns once the snapshot has been = scheduled to be destroyed, not after the snapshot has been completely = destroyed. How big are these datasets and snapshots ?