Date: Tue, 22 Jan 2013 15:02:40 -0800 From: Freddie Cash <fjwcash@gmail.com> To: Warren Block <wblock@wonkity.com> Cc: FreeBSD Filesystems <freebsd-fs@freebsd.org>, Scott Long <scottl@samsco.org> Subject: Re: RFC: Suggesting ZFS "best practices" in FreeBSD Message-ID: <CAOjFWZ4X8src2DQV%2B49DjKgT7pgMbR69j%2BiRAq-UoVA0Lz3xcg@mail.gmail.com> In-Reply-To: <alpine.BSF.2.00.1301220759420.61512@wonkity.com> References: <314B600D-E8E6-4300-B60F-33D5FA5A39CF@sarenet.es> <alpine.BSF.2.00.1301220759420.61512@wonkity.com>
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On Jan 22, 2013 7:04 AM, "Warren Block" <wblock@wonkity.com> wrote: > > On Tue, 22 Jan 2013, Borja Marcos wrote: > >> 1- Dynamic disk naming -> We should use static naming (GPT labels, for instance) >> >> ZFS was born in a system with static device naming (Solaris). When you plug a disk it gets a fixed name. As far as I know, at least from my experience with Sun boxes, c1t3d12 is always c1t3d12. FreeBSD's dynamic naming can be very problematic. >> >> For example, imagine that I have 16 disks, da0 to da15. One of them, say, da5, dies. When I reboot the machine, all the devices from da6 to da15 will be renamed to the device number -1. Potential for trouble as a minimum. >> >> After several different installations, I am preferring to rely on static naming. Doing it with some care can really help to make pools portable from one system to another. I create a GPT partition in each drive, and Iabel it with a readable name. Thus, imagine I label each big partition (which takes the whole available space) as pool-vdev-disk, for example, pool-raidz1-disk1. > > > 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? The ZFS metadata on disk allows you to move disks around in a system and still import the pool, correct. But the ZFS metadata will not help you figure out which disk, in which bay, of which drive shelf just died and needs to be replaced. That's where glabels, gpt labels, and similar come in handy. It's for the sysadmin, not the system itself.
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