Date: Wed, 8 Oct 2008 11:45:14 +0200 From: Michel Talon <talon@lpthe.jussieu.fr> To: freebsd-questions@freebsd.org Subject: Re: adding a slice to gmirror instead of a whole disk, will it work? Message-ID: <20081008094514.GA96151@lpthe.jussieu.fr>
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Craig Butler wrote: > Will adding a slice to a gmirror instead of a whole disk work? > The slice is big enough to accommodate the old disk. It will work no problem. The only possible trouble is to have the last sector of the disk or slice free to be able to put the geom marker on it. For example i have a mirror with 2 slices: asmodee% gmirror list Geom name: gms1 State: COMPLETE Components: 2 Balance: load Slice: 4096 Flags: NONE GenID: 0 SyncID: 2 ID: 1193348252 Providers: 1. Name: mirror/gms1 Mediasize: 16776699904 (16G) Sectorsize: 512 Mode: r5w5e5 Consumers: 1. Name: ad0s1 Mediasize: 16776700416 (16G) Sectorsize: 512 Mode: r1w1e1 State: ACTIVE Priority: 0 Flags: DIRTY GenID: 0 SyncID: 2 ID: 1158494643 2. Name: ad4s1 Mediasize: 16776700416 (16G) Sectorsize: 512 Mode: r1w1e1 State: ACTIVE Priority: 0 Flags: DIRTY GenID: 0 SyncID: 2 ID: 2277636746 Note that in this case (one of the disks is slower than the other) i observed that the "round-robin" strategy was giving poor results (slower than the slowest of the two disks) while the "load" strategy gives performance like the faster disk. Consumers can be absolutely anything, this is the beauty of the GEOM idea. -- Michel TALON
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