Date: Sun, 4 Sep 2016 14:11:37 -0400 From: Paul Kraus <paul@kraus-haus.org> To: FreeBSD FS <freebsd-fs@freebsd.org> Subject: Re: phantom snapshots Message-ID: <8B542627-1FBA-469D-BAAE-60C9BB615326@kraus-haus.org> In-Reply-To: <bbb97a59-df1c-4ffc-f41b-953b0018c903@kateley.com> References: <58816ff0-3ab2-cbae-3d50-c4d5e89d9773@kateley.com> <57C9D1FB.6040904@b1t.name> <bbb97a59-df1c-4ffc-f41b-953b0018c903@kateley.com>
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> On Sep 2, 2016, at 3:41 PM, Linda Kateley <lkateley@kateley.com> = 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 <snapshot> 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 ?
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