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ZFS/zfs-shrinkpool-demo.sh

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+#!/bin/bash5
+
+# NOTE this only works on MIRROR pools, NOT RAIDZ
+
+# REF: https://askubuntu.com/questions/1231355/how-can-i-shrink-a-zfs-volume-on-ubuntu-18-04
+# Tested with zfs 1.9.4 on OSX High Sierra 10.13 (approx. == ZFS 0.8.6 on Linux)
+
+#source ~/bin/failexit.mrg
+# REF: https://sharats.me/posts/shell-script-best-practices/
+function failexit () {
+  echo '! Something failed! Code: '"$1 $2" >&2 # code (and optional description)
+  exit $1
+}
+
+# TODO EDITME xxx
+dest=/Volumes/sgtera2
+iso2cp=/Volumes/ztoshtera10/shrcompr-ztoshtera10/ISO/systemrescue-9.06-amd64.iso
+
+cd $dest || failexit 44 "Cant cd to $dest"
+
+echo "$(date) - Creating virtual zfs disks"
+size2=4096
+size1=2048
+
+time truncate -s ${size1}M zd1                               
+truncate -s ${size1}M zd2
+truncate -s ${size1}M zd3
+truncate -s ${size1}M zd4
+
+time truncate -s ${size2}M zd5
+truncate -s ${size2}M zd6
+truncate -s ${size2}M zd7
+time truncate -s ${size2}M zd8
+
+ls -lh zd*
+date
+
+[ -e zd1 ] || failexit 45 "Cant find zd disks in $dest"
+
+zp=zshrinky
+echo "$(date) - Creating zpool $zp"
+
+zpool create -f -o ashift=12 -O atime=off -O compression=lz4 $zp mirror \
+ $PWD/zd5 $PWD/zd6 || failexit 64 "Failed to create $zp"
+zpool set autoexpand=on $zp
+
+gdf -hT /Volumes/$zp
+echo "$(date) - Copying ISO to $zp"
+time cp -v $iso2cp /Volumes/$zp
+ls -lh /Volumes/$zp
+
+function zps () {
+ zpool status -v $zp |awk 'NF>0'
+}
+
+zps
+zpool list $zp
+
+echo "Press Enter to shrink - existing pool is ~ ${size2}M - or ^C to stop"
+read
+
+echo "$(date) - Adding smaller mirror disks"
+zpool add $zp mirror $PWD/zd1 $PWD/zd2
+zps
+
+echo "$(date) - Shrinkydink"
+time zpool remove $zp mirror-0
+
+date
+
+while :; do
+  [ $(zps |grep -c "Evacuation of mirror in progress") -eq 0 ] && break
+  zps
+  zpool iostat -y -T d -v $zp
+  sleep 5
+done
+
+echo "- DONE -"
+zps 
+echo ''
+zpool list $zp
+echo ''
+gdf -hT /Volumes/$zp
+date
+
+exit;
+
+
+# Example output
+  pool: zshrinky
+ state: ONLINE
+  scan: none requested
+remove: Removal of vdev 0 copied 744M in 0h0m, completed on Wed Apr 26 00:08:13 2023
+    18.2K memory used for removed device mappings
+config:
+        NAME                      STATE     READ WRITE CKSUM
+        zshrinky                  ONLINE       0     0     0
+          mirror-1                ONLINE       0     0     0
+            /Volumes/sgtera2/zd1  ONLINE       0     0     0
+            /Volumes/sgtera2/zd2  ONLINE       0     0     0
+errors: No known data errors
+
+NAME       SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP  HEALTH  ALTROOT
+zshrinky  1.88G   745M  1.15G        -         -     5%    38%  1.00x  ONLINE  -
+
+Filesystem     Type  Size  Used Avail Use% Mounted on
+zshrinky       zfs   1.8G  744M  1.1G  42% /Volumes/zshrinky