Date: Sun, 12 Jun 2016 19:47:17 -0500 From: Brandon J. Wandersee <brandon.wandersee@gmail.com> To: Yuri <yuri@rawbw.com> Cc: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Re: ZFS: Is 'zpool add' really irreversible? Message-ID: <864m8xewyy.fsf@WorkBox.Home> In-Reply-To: <22e9b8aa-3171-f399-f3a8-b71eb92210f5@rawbw.com> References: <d13abf72-3903-796a-1d47-e3a7b776ebf8@rawbw.com> <86shwiax38.fsf@WorkBox.Home> <22e9b8aa-3171-f399-f3a8-b71eb92210f5@rawbw.com>
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Yuri writes: > People may reasonably want to remove some disks in some layouts, due > to failures, etc, and ZFS just lacks the flexibility to do that. Obviously, if you're dealing with any sort of RAID you'll occasionally be replacing failed disks; ZFS is no different, and you can swap out disks while the system is running. You just can't remove a *virtual device*. You can't just shuffle disks around willy-nilly, because you'd effectively destroy the storage pool in the process. There's a minimum number of disks that need to be attached, and that minimum changes as you add virtual (not necessarily physical) devices to a pool. Traditional RAID has the same sort of limitation: create a RAID 5 array out of three disks, then remove two disks. You've just destroyed the array. If you want to temporarily add a single disk to a system, you can just create a second pool on it. There's no arbitrary limit to how many pools a system can have. ZFS has real limitations, but they're not that strict. -- :: Brandon J. Wandersee :: brandon.wandersee@gmail.com :: -------------------------------------------------- :: 'The best design is as little design as possible.' :: --- Dieter Rams ----------------------------------
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