Date: Wed, 08 Aug 2012 10:05:10 +0200 From: "Ronald Klop" <ronald-freebsd8@klop.yi.org> To: freebsd-fs@freebsd.org Subject: Re: ZFS questions Message-ID: <op.wipp2wx28527sy@ronaldradial.versatec.local> In-Reply-To: <201208080424.q784OEfY051025@gw.catspoiler.org> References: <201208080424.q784OEfY051025@gw.catspoiler.org>
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On Wed, 08 Aug 2012 06:24:14 +0200, Don Lewis <truckman@freebsd.org> wrote: > I've got a couple of questions about a raidz array that I'm putting > together. Capacity is more important to me than speed, but I don't want > to do anything too stupid. > > The fine manual says that using whole disks is preferable to using > slices because drive write-caching is enabled if the entire drive is > dedicated to ZFS, which would break things if the drive also contained a > UFS slice. Does this really matter much if NCQ is available? Each > drive will be dedicated to ZFS, but I'm planning on using GPT to > slightly undersize the the ZFS slice on each drive to avoid any > potential issues of installing replacement drives that are slightly > smaller than the original drives. Solaris does/did this. FreeBSD does not disable the write-cache if you don't use the whole disk. > I'm slowly accumulating the drives over time for both budgetary reasons > and to also try to reduce the chances of multiple near-simultaneous > failures of drives from the same manufacturing batch. I'd like to get > the array up and running before I have all the drives, but unfortunately > ZFS doesn't allow new drives to be added to an existing raidz vdev to > increase its capacity. I do have some smaller drives and I was thinking > about pairing those up with gconcat or gstripe and configuring the ZFS > pool with the concatenated/striped pairs. I know this isn't > recommended, but it seems to me like zpool create would accept this. > What concerns me is happens on reboot when ZFS goes searching for all of > the components of its pool. Will it stumble across its metadata on the > first of the two concatenated pairs and try to add that individual drive > to the pool instead of the pair? I don't know. Somebody else might answer this. Ronald.
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