Date: Sun, 3 Oct 2021 06:33:53 +0100 From: Steve O'Hara-Smith <steve@sohara.org> To: David Christensen <dpchrist@holgerdanske.com> Cc: freebsd-questions@freebsd.org Subject: Re: zfs q regarding backup strategy Message-ID: <20211003063353.7415d12917f0e514d433ae1c@sohara.org> In-Reply-To: <69954781-9e3c-ba96-5f1e-9b4043ecf56c@holgerdanske.com> References: <YVZM1HnPuwIUQpah@ceres.zyxst.net> <ba54a415-da45-e662-73fe-65702c4131e2@holgerdanske.com> <YVcXsF5NFq2abE%2B7@ceres.zyxst.net> <20211001222816.a36e9acbd4e8829aed3afb68@sohara.org> <809e4f3b-9e59-eb53-5b7d-0bcf7e401cd5@holgerdanske.com> <20211002115440.85c4342a49fe6e4573c37dd0@sohara.org> <daf9ba49-82a3-670c-f59c-745e0c315f18@holgerdanske.com> <20211002205504.9d81ee94caa231ee9b008d6a@sohara.org> <69954781-9e3c-ba96-5f1e-9b4043ecf56c@holgerdanske.com>
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On Sat, 2 Oct 2021 15:09:23 -0700 David Christensen <dpchrist@holgerdanske.com> wrote: > Assuming I can create a ZFS pool from one or more ZFS volume datasets > (?), here is an idea: I don't think you can create a pool on top of zvols, I couldn't get it to work last time I tried. > 1. Create a large 'archive' pool. Say, 10 TB. > > 2. Within the archive pool, create many small volumes. Say, 100 > volumes of 100 GB each. Why not just split the drives into 100GB partitions with gpart rather than attempting to nest zpools ? > 3. For each source, create a 'archive-source' pool using the 'zpool > create -R' option and one or more volumes as required for capacity. Also record the root mount for use at boot time. > 4. From the archive server, replicate datasets from their respective > source pools to their corresponding archive-source pools using the 'zfs > receive -u' option. Once you have altroot working then you want the dataset mounted - read only though. > 5. Upon receipt of a replica dataset, save the 'canmount' property (for > restore). If it is 'on', set it to 'notauto'. No need. > 6. Upon receipt of a replica dataset, save the 'readonly' property (for > restore). If it is 'off', set it to 'on'. Yes. It is also necessary to check to see whether the target pool has enough space and if not throw a few more logs on the fire. > The most obvious problem is if the system crashes between #4 and #5. On > subsequent boot, AIUI all previously active pools will be automatically > imported (e.g. without 'altroot') and all datasets with 'canmount=on' > will be mounted (according to 'mountpoint'). If two or more datasets > are mounted at the same mount point, the results could be bad. > 'bootpool' and 'zroot' are likely cases. This is where the boot script to restore the altroot settings comes in - but it has to run before zfs attempts the mounts. -- Steve O'Hara-Smith <steve@sohara.org>
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