Date: Sun, 22 Mar 2009 10:07:40 +0100 From: Ulrich =?utf-8?B?U3DDtnJsZWlu?= <uspoerlein@gmail.com> To: Pete French <petefrench@ticketswitch.com>, freebsd-stable@freebsd.org Subject: Re: gemor mirror and priority Message-ID: <20090322090740.GA1519@roadrunner.spoerlein.net> In-Reply-To: <20090321184440.GA29399@lava.net> References: <B1A41ABF-538C-49F3-A10C-F1E60D56467E@moneybookers.com> <E1Lkigc-000BOY-HL@dilbert.ticketswitch.com> <20090321184440.GA29399@lava.net>
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On Sat, 21.03.2009 at 08:44:42 -1000, Clifton Royston wrote: > Even if you don't, I think it's quite useful to make the *default* > priority set when creating a mirror be some value which allows both > higher and lower values to be specified. I hadn't known about that > issue until I read the original thread here a while back.If the default > were set to some mid-range value, or even to 2, for example, then at > least creating a new mirror and adding drives without setting a > priority would continue to behave as usual, while it would be possible > to explicitly insert new components with a lower priority. (I see why > one wouldn't want to change the default interpretation of existing > priority values for POLA reasons.) > > There are lots of reasons one could want to control priorities of > mirrored drives in various ways. One is to use gmirror as a long-term > backup approach: mirror with three drives, periodically disconnecting > one from the mirror to swap it with a fresh drive from a pool of backup > drives. I haven't tried this, but it's been on my mind to mess around > with soon. I did this for 2-3 years and it has worked very well. Of course I took care of using the right priorities from the start. This setup has now been replaced by a ZFS mirror. The resilver time is just so much better :) > In this case, I would want the designated backup drive to always be > lowest-priority, to ensure the mirror never accidentally started > rebuilding from a newly reinserted backup. (This probably wouldn't > happen anyway, but it would be nice to be sure...) This will not happen. Besides, I would strongly encourage you to disable automatic rebuilding for this type of setup. Cheers, Ulrich Spörlein -- None are more hopelessly enslaved than those who falsely believe they are free -- Johann Wolfgang von Goethe
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