Date: Tue, 6 Apr 2021 11:53:00 -0700 From: David Christensen <dpchrist@holgerdanske.com> To: freebsd-questions@freebsd.org Subject: Re: advise or best practices with ZFS snapshot Message-ID: <52857d52-152e-335f-cb9a-97f342dc006b@holgerdanske.com> In-Reply-To: <MX_GFO7--B-2@keemail.me> References: <MX_GFO7--B-2@keemail.me>
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On 4/5/21 8:41 PM, sesquivels--- via freebsd-questions wrote: > Geom name: ada1 > Providers: > 1. Name: ada1 > Mediasize: 128035676160 (119G) > Sectorsize: 512 > Mode: r1w1e2 > descr: MTFDDAK128MAM-1J1 > lunid: 500a0751039d7440 > ident: 1405039D7440 > rotationrate: 0 > fwsectors: 63 > fwheads: 16 What is this drive used for? > zpool status > pool: zroot > state: ONLINE > scan: scrub repaired 0 in 0 days 01:43:28 with 0 errors on Thu Mar 18 01:57:21 2021 > config: > > NAME STATE READ WRITE CKSUM > zroot ONLINE 0 0 0 > raidz1-0 ONLINE 0 0 0 > ada4p3 ONLINE 0 0 0 > ada5p3 ONLINE 0 0 0 > ada6p3 ONLINE 0 0 0 > ada7p3 ONLINE 0 0 0 > raidz1-2 ONLINE 0 0 0 > ada0 ONLINE 0 0 0 > ada2 ONLINE 0 0 0 > ada3 ONLINE 0 0 0 > ada8 ONLINE 0 0 0 > logs > nvd0p2 ONLINE 0 0 0 > cache > nvd0p1 ONLINE 0 0 0 > > errors: No known data errors So, your pool is comprised of two raidz1 vdevs of 4 @ 1 TB each, an NVMe partition for log, and an NVMe partition for cache. OS pools are named 'zpool' by the FreeBSD installer. Data pools are conventionally named 'tank' (I use the letter 'p' followed by a unique number). This article has some good ideas: https://b3n.org/zfs-hierarchy/ Is the above your OS pool? If your log device fails, you may lose data. The recommended practice is to use a vdev with redundancy for the log (e.g. 2 drive mirror, 3 drive raidz1, etc.). https://docs.oracle.com/cd/E19253-01/819-5461/gazgw/index.html Using a partition on your NVMe device for the cache should help performance. > About zfs administration, and snapshots, where can I found more information? I like the books by Lucas: https://mwl.io/nonfiction/os#af3e https://mwl.io/nonfiction/os#fmzfs https://mwl.io/nonfiction/os#fmaz > https://docs.oracle.com/cd/E19253-01/819-5461/gbiqe/index.html > zfs list -t snapshot > NAME USED AVAIL REFER MOUNTPOINT > zroot/Dom@03252021 32.6G - 353G - My pools were created with early versions of FreeBSD 11R and 12R, and do not have the 'listsnapshots' property. This is how I look at snapshots of a given filesystem: 2021-04-06 09:48:42 toor@f3 ~ # zfs list -t all -d 1 p3/ds2 | grep @ | tail p3/ds2@manual-20210217-1553 0 - 88K - p3/ds2@manual-20210226-2334 0 - 88K - p3/ds2@manual-20210228-1807 0 - 88K - p3/ds2@manual-20210301-1524 0 - 88K - p3/ds2@manual-20210306-0009 0 - 88K - p3/ds2@manual-20210314-1201 0 - 88K - p3/ds2@manual-20210321-1355 0 - 88K - p3/ds2@manual-20210328-1520 0 - 88K - p3/ds2@manual-20210328-2306 0 - 88K - p3/ds2@manual-20210404-1338 0 - 88K - > https://docs.oracle.com/cd/E18752_01/html/819-5461/gbchx.html > Doing a zfs send to file as this, may I delete [snapshot] from my zpool and then restore it using zfs receiver? > zfs send zroot/Dom@03252021 | gzip > /mnt/bkp/march2021.gz Do you understand that the above command will not backup any child filesystems of zroot/Dom? Nor any other snapshots? If and when you restore that filesystem, you may want to validate it. mtree(8) is one option: https://www.techrepublic.com/blog/it-security/use-mtree-for-filesystem-integrity-auditing/ Once you figure out how to properly backup, restore, and validate your filesystem(s), you will need to think about backup redundancy and aging policies. I would retain snapshots on the live system until it needed more space. I would retain backup files on the backup device or system until it needed more space. Are you aware of zfs-auto-snapshot? # pkg install zfstools zfs-auto-snapshot is configured via crontab(1): 2021-04-06 10:30:36 toor@f3 ~ # crontab -l | grep ds2 3 * * * * /usr/local/sbin/zfs-auto-snapshot -P p3/ds2 -k h 24 15 3 * * 0 /usr/local/sbin/zfs-auto-snapshot -P p3/ds2 -k w 4 21 3 1 * * /usr/local/sbin/zfs-auto-snapshot -P p3/ds2 -k m 24 27 3 1 1 * /usr/local/sbin/zfs-auto-snapshot -P p3/ds2 -k y 99 and via ZFS properties: 2021-04-06 10:33:05 toor@f3 ~ # zfs get all p3 p3/ds2 | grep auto-snapshot p3 com.sun:auto-snapshot true local p3/ds2 com.sun:auto-snapshot true inherited from p3 I write scripts for repetitive operations to get accuracy and consistency. My collection of scripts has grown and evolved as I have learned. ZFS may appear simple going in, but is non-trivial in practice. I had more than a few painful accidents early on. I suggest that you build a virtual machine, some pools, and some filesystems to learn and practice with. Go through the various use-cases and make sure that you understand what is happening before you attempt them on live data. David
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