Date: Wed, 23 Apr 2014 17:20:56 +0100 From: Tom Evans <tevans.uk@googlemail.com> To: Karl Denninger <karl@denninger.net> Cc: FreeBSD FS <freebsd-fs@freebsd.org> Subject: Re: ZFS unable to import pool Message-ID: <CAFHbX1JoetKbXd9cykhcro0xbKgvrb1uCzD_moC=Wgr01jfEdA@mail.gmail.com> In-Reply-To: <5357D7E7.605@denninger.net> References: <B493BD80-CDC2-4BA6-AC14-AE16B373A051@icloud.com> <20140423064203.GD2830@sludge.elizium.za.net> <B1024D84-EBBE-4A9B-82C4-5C19B5A66B60@icloud.com> <20140423080056.GE2830@sludge.elizium.za.net> <20140423091852.GH2830@sludge.elizium.za.net> <20140423100126.GJ2830@sludge.elizium.za.net> <5357937D.4080302@gmail.com> <72E79259-3DB1-48B7-8E5E-19CC2145A464@icloud.com> <888649C4-CC66-48A6-9901-BEA93D1BBFA3@mail.turbofuzz.com> <FC0D5991-8F8D-41D5-BB50-AB840C29F362@icloud.com> <5357CC7B.2090003@denninger.net> <CAFHbX1Lh7qCsE%2Bgxmf9jBcu5c1Wr_ApHB9SP_VWYnkNj3N_5HQ@mail.gmail.com> <5357D7E7.605@denninger.net>
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On Wed, Apr 23, 2014 at 4:10 PM, Karl Denninger <karl@denninger.net> wrote: > I have a large home system as well. > > But I do back it up to other spinning pieces of rust, and rotate the backups > out to a bank safe-deposit box. If I make a terrible mistake (or my > hardware and/or software does) I have a means of recovery. There are no > guarantees of course in that I COULD wind up with a bad disk in the safe > deposit box, but if my house burns down I have a shot at recovery with high > odds of success -- an act that would otherwise be impossible. Partitioning > my data off into "essentially archival, read-almost-only" and "active" means > that the former needs to be updated rarely and the former is of small enough > size that I don't go crazy doing it either in money or time. I recently re-jigged my setup to do just this - the root pool and working set are on a pair of SSDs, and the rarely written and seldom read data lives on a special archive pool - 8 disk raidz2. > > And I *HAVE* had things like this happen -- twice in the last 20 years I've > had a disk adapter go insane and scribble on MULTIPLE spindles at once. > There is no RAID strategy that will protect you against this event; you > either have a backup or you're done. I didn't want to know that :) > > ZFS actually makes this easier with send/receive and the ability to import a > pool, send to it and then export it. The backup pool can have compression > turned on where for performance reasons it may not make sense for the online > pool to do so. And you can rotate that out fairly easily too; you can take > a 2-way mirror, add a third disk and let it resilver, then split the third > one off and remove it, giving you a dismounted copy you can then stick in a > box and yet if you need it -- it's there. I should be doing more of this, although it is trickier to do with a large pool. Splitting my datasets in to smaller chunks would help to backup to dismounted pools. Interesting advice, thanks Karl! Cheers Tom
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