Date: Thu, 16 May 2019 02:36:07 +0200 From: Peter <pmc@citylink.dinoex.sub.org> To: Miroslav Lachman <000.fbsd@quip.cz> Cc: freebsd-fs@freebsd.org Subject: Re: Waht is the minimum free space between GPT partitions? Message-ID: <20190516003607.GA93284@gate.oper.dinoex.org> In-Reply-To: <60d57363-eb5c-e985-82ad-30f03b06a4c6@quip.cz> References: <20190515204243.GA67445@gate.oper.dinoex.org> <60d57363-eb5c-e985-82ad-30f03b06a4c6@quip.cz>
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On Thu, May 16, 2019 at 12:29:16AM +0200, Miroslav Lachman wrote: ! > I found, if I put partitions directly together (so that another starts ! > immediately after one ends), under certain circumstances the volumes ! > become inaccessible and the system (11.2) does crash. Obviousely there ! > is a safety distance required - but how big should it be? ! ! I read your post on forum ! https://forums.freebsd.org/threads/create-degraded-raid-5-with-2-disks-on-freebsd.70750/#post-426756 Hi, great, that should explain how to make it happen. ! No problems for years. Me neither with MBR/packlabels, but only recently switched to GPT. I suppose either GPT or ZFS-autoexpand seems to go out-of-bounds; I couldn't determine which. ! I think your case is somewhat different if you split disk in to 3 ! partitions later used as 3 devices for one ZFS pool, so maybe there is ! some coincidence with expanding ZFS... and then it is a bug which should ! be fixed. If we could fix it that would be even better! Agreed, it's an ugly operation, but I love to do ugly things with ZFS, and usually it stands it. ;) ! Can you prepare some simple testcase (scriptable) which make a panic on ! your host? I will try it in some spare VM. The description in mentioned forum-post is pretty much what I did. At first I did it on my router, as there is empty space on a disk, and when that had gone by-by, I tried it on the desktop with an (otherwise empty) USB stick. Takes an eternity to create ZFS-raidz even on USB-3 stick - they are not designed for that - but the outcome was the same. Procedure is: 1. create new GPT scheme on stick. 2. add 3x 1G freebsd-zfs partitions with 1G -free- in between. 3. zpool create test raidz da0p1 da0p2 da0p3 4. resize 3x partitions to 2G each 5. zpool set autoexpand=on test 6. export the pool 7. zpool online At that point it will start to complain that (some of) the pool isn't readable. Now resize the partitions back to 1G. -> kernel crash And after going thru that and having all partitions back at 1G, the pool works again. :) I'll try to reproduce it from a script, as soon as my toolchain is done with building from the recent patches. Cheerio, PMc
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