Date: Tue, 22 Jan 2013 19:16:25 -0700 (MST) From: Warren Block <wblock@wonkity.com> To: Michael DeMan <freebsd@deman.com> Cc: FreeBSD Filesystems <freebsd-fs@freebsd.org> Subject: Re: RFC: Suggesting ZFS "best practices" in FreeBSD Message-ID: <alpine.BSF.2.00.1301221907120.66546@wonkity.com> In-Reply-To: <B60D815C-3F2D-4FA7-B5CC-D04EC262853B@deman.com> References: <314B600D-E8E6-4300-B60F-33D5FA5A39CF@sarenet.es> <alpine.BSF.2.00.1301220759420.61512@wonkity.com> <B60D815C-3F2D-4FA7-B5CC-D04EC262853B@deman.com>
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On Tue, 22 Jan 2013, Michael DeMan wrote: > On Jan 22, 2013, at 7:04 AM, Warren Block <wblock@wonkity.com> wrote: >> >> I'm a proponent of using various types of labels, but my impression >> after a recent experience was that ZFS metadata was enough to >> identify the drives even if they were moved around. That is, ZFS >> bare metadata on a drive with no other partitioning or labels. >> >> Is that incorrect? > > I don't know if it is correct or not, but the best I could figure out > was to both label the drives and also force the mapping so the > physical and logical drives always show up associated correctly. I > also ended up deciding I wanted the hostname as a prefix for the > labels - so if they get moved around to say another machine I can look > and know what is going on - 'oh yeah, those disks are from the ones we > moved over to this machine'... It helps to avoid duplicate labels, a good idea. > #1. Map the physical drive slots to how they show up in FBSD so if a > disk is removed and the machine is rebooted all the disks after that > removed one do not have an 'off by one error'. i.e. if you have > ada0-ada14 and remove ada8 then reboot - normally FBSD skips that > missing ada8 drive and the next drive (that used to be ada9) is now > called ada8 and so on... How do you do that? If I'm in that situation, I think I could find the bad drive, or at least the good ones, with diskinfo and the drive serial number. One suggestion I saw somewhere was to use disk serial numbers for label values. > #2. Use gpart+gnop to deal with 4K disk sizes in a standardized way > and also to leave a little extra room so if when doing a replacement > disk and that disk is a few MB smaller than the original - it all > 'just works'. (All disks are partitioned to a slightly smaller size > than their physical capacity). I've been told (but have not personally verified) that newer versions of ZFS actually leaves some unused space at the end of a drive to allow for variations in nominally-sized drives. Don't know how much.
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