I notice that Unbuntu now offers ZFS as an option for installation. I use btrfs, but I keep hearing about ZFS and wonder which file system is better. Any feedback from those who have used both?
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I haven't used ZFS, and won't consider it because I'm allergic to anything from Oracle.Regards, John LittleComment
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Personally, I think it's a "use case" issue. I'm using BTRFS on my 20.04, but I don't do any backups; it's my laptop, and NOT my primary *buntu OS, so I "don't care" if I have to wipe it and reinstall.Originally posted by oldgeek View PostWindows no longer obstructs my view.
Using Kubuntu Linux since March 23, 2007.
"It is a capital mistake to theorize before one has data." - Sherlock HolmesComment
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Funny you should mention that. Earlier today I downloaded the Ubuntu 20.04 ISO with the deliberate purpose of installing it as a VM using ZFS as the root file system. I have done that and have begun learning how to use it.Originally posted by oldgeek View Post
I plan to post my experiences in the BTRFS forum which Oshunluver linked to, unless the admins create a ZFS subforum.
BTW, Sun open sourced Solaris and ZFS in 2005 under the CDDL license. IN 2010 Oracle bought Sun and stopped updating the ZFS so a company whose name I forgot took the CDDL source code and began maintaining it. In 2013 OpenZFS was formed and is now the entity responsible for maintaining and developing the code. Oracle has nothing to do with it and cannot shut it down as long as the devs use green room techniques.
Canonical has decided that the CDDL isn't enough of a hindrance to not add it to their release. So they added it.
When you get to the section of the installer where you choose what device you are going to install Ubuntu on there is a radio button labeled "Advanced". Click it and you are on your way to making ZFS the <ROOT_FS> of your installation.
In the days and weeks ahead, if I maintain an interest in it, I will be posting my experiences.
So far, I can say this: running a VM of Ubuntu 20.04 on ZFS is no slower than running a VM of UbuntuDDE on EXT4. I gave ZFS only 30GB of vdisk1, 4K of RAM and 2 cores, but it is fairly fast, once it finishes loading. The systemd-analyze time to a working DE is 25.4 seconds. Also, "systemctl list-unit-files" does not list any of the snapd loops or loop mount points that Kubuntu lists, but snapd daemons are present. I searched the "Store" high and low for zfs-auto-snapshot but couldn't find it. So, assuming it was in the repository, but not the one the store was using, I gave the terminal a chance to find it. "sudo apt install zfs-auto-snapshot" installed it quickly from the CLI.
Here is a list of the bpool and rpool (b for boot and r for root)
Here is the snapshot listing:Code:jerry@jerry-Standard-PC-Q35-ICH9-2009:~$[B] zfs list[/B] NAME USED AVAIL REFER MOUNTPOINT bpool 90.8M 1.16G 96K /boot bpool/BOOT 90.1M 1.16G 96K none bpool/BOOT/ubuntu_z6p9vy 90.0M 1.16G 90.0M /boot rpool 3.47G 22.2G 96K / rpool/ROOT 3.34G 22.2G 96K none rpool/ROOT/ubuntu_z6p9vy 3.34G 22.2G 2.42G / rpool/ROOT/ubuntu_z6p9vy/srv 96K 22.2G 96K /srv rpool/ROOT/ubuntu_z6p9vy/usr 224K 22.2G 96K /usr rpool/ROOT/ubuntu_z6p9vy/usr/local 128K 22.2G 128K /usr/local rpool/ROOT/ubuntu_z6p9vy/var 792M 22.2G 96K /var rpool/ROOT/ubuntu_z6p9vy/var/games 96K 22.2G 96K /var/games rpool/ROOT/ubuntu_z6p9vy/var/lib 780M 22.2G 678M /var/lib rpool/ROOT/ubuntu_z6p9vy/var/lib/AccountsService 208K 22.2G 96K /var/lib/AccountsService rpool/ROOT/ubuntu_z6p9vy/var/lib/NetworkManager 500K 22.2G 124K /var/lib/NetworkManager rpool/ROOT/ubuntu_z6p9vy/var/lib/apt 56.3M 22.2G 51.4M /var/lib/apt rpool/ROOT/ubuntu_z6p9vy/var/lib/dpkg 39.5M 22.2G 32.6M /var/lib/dpkg rpool/ROOT/ubuntu_z6p9vy/var/log 12.0M 22.2G 5.97M /var/log rpool/ROOT/ubuntu_z6p9vy/var/mail 96K 22.2G 96K /var/mail rpool/ROOT/ubuntu_z6p9vy/var/snap 256K 22.2G 112K /var/snap rpool/ROOT/ubuntu_z6p9vy/var/spool 280K 22.2G 112K /var/spool rpool/ROOT/ubuntu_z6p9vy/var/www 96K 22.2G 96K /var/www rpool/USERDATA 126M 22.2G 96K / [B]rpool/USERDATA/jerry_0mgvki 126M 22.2G 87.0M /home/jerry[/B] rpool/USERDATA/root_0mgvki 104K 22.2G 104K /root jerry@jerry-Standard-PC-Q35-ICH9-2009:~$
You'll notice that there appears to be a lot of redundant snapshotting. My /home/jerry subvolume,Code:jerry@jerry-Standard-PC-Q35-ICH9-2009:~$ zfs list -t snapshot NAME USED AVAIL REFER MOUNTPOINT bpool/BOOT/ubuntu_z6p9vy@autozsys_ps1e80 0B - 90.0M - bpool/BOOT/ubuntu_z6p9vy@autozsys_kqk0hl 0B - 90.0M - bpool/BOOT/ubuntu_z6p9vy@autozsys_2ivctg 0B - 90.0M - bpool/BOOT/ubuntu_z6p9vy@autozsys_3f11n0 0B - 90.0M - bpool/BOOT/ubuntu_z6p9vy@autozsys_lv1ui9 0B - 90.0M - rpool/ROOT/ubuntu_z6p9vy@autozsys_ps1e80 0B - 2.40G - rpool/ROOT/ubuntu_z6p9vy@autozsys_kqk0hl 0B - 2.40G - rpool/ROOT/ubuntu_z6p9vy@autozsys_2ivctg 1.13M - 2.41G - rpool/ROOT/ubuntu_z6p9vy@autozsys_3f11n0 23.4M - 2.44G - rpool/ROOT/ubuntu_z6p9vy@autozsys_lv1ui9 45.9M - 2.42G - rpool/ROOT/ubuntu_z6p9vy/srv@autozsys_ps1e80 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/srv@autozsys_kqk0hl 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/srv@autozsys_2ivctg 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/srv@autozsys_3f11n0 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/srv@autozsys_lv1ui9 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/usr@autozsys_ps1e80 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/usr@autozsys_kqk0hl 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/usr@autozsys_2ivctg 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/usr@autozsys_3f11n0 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/usr@autozsys_lv1ui9 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/usr/local@autozsys_ps1e80 0B - 128K - rpool/ROOT/ubuntu_z6p9vy/usr/local@autozsys_kqk0hl 0B - 128K - rpool/ROOT/ubuntu_z6p9vy/usr/local@autozsys_2ivctg 0B - 128K - rpool/ROOT/ubuntu_z6p9vy/usr/local@autozsys_3f11n0 0B - 128K - rpool/ROOT/ubuntu_z6p9vy/usr/local@autozsys_lv1ui9 0B - 128K - rpool/ROOT/ubuntu_z6p9vy/var@autozsys_ps1e80 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var@autozsys_kqk0hl 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var@autozsys_2ivctg 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var@autozsys_3f11n0 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var@autozsys_lv1ui9 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/games@autozsys_ps1e80 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/games@autozsys_kqk0hl 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/games@autozsys_2ivctg 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/games@autozsys_3f11n0 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/games@autozsys_lv1ui9 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/lib@autozsys_ps1e80 0B - 434M - rpool/ROOT/ubuntu_z6p9vy/var/lib@autozsys_kqk0hl 0B - 434M - rpool/ROOT/ubuntu_z6p9vy/var/lib@autozsys_2ivctg 184K - 434M - rpool/ROOT/ubuntu_z6p9vy/var/lib@autozsys_3f11n0 156K - 434M - rpool/ROOT/ubuntu_z6p9vy/var/lib@autozsys_lv1ui9 2.13M - 436M - rpool/ROOT/ubuntu_z6p9vy/var/lib/AccountsService@autozsys_ps1e80 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/lib/AccountsService@autozsys_kqk0hl 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/lib/AccountsService@autozsys_2ivctg 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/lib/AccountsService@autozsys_3f11n0 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/lib/AccountsService@autozsys_lv1ui9 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/lib/NetworkManager@autozsys_ps1e80 0B - 124K - rpool/ROOT/ubuntu_z6p9vy/var/lib/NetworkManager@autozsys_kqk0hl 0B - 124K - rpool/ROOT/ubuntu_z6p9vy/var/lib/NetworkManager@autozsys_2ivctg 96K - 132K - rpool/ROOT/ubuntu_z6p9vy/var/lib/NetworkManager@autozsys_3f11n0 96K - 132K - rpool/ROOT/ubuntu_z6p9vy/var/lib/NetworkManager@autozsys_lv1ui9 96K - 132K - rpool/ROOT/ubuntu_z6p9vy/var/lib/apt@autozsys_ps1e80 0B - 55.7M - rpool/ROOT/ubuntu_z6p9vy/var/lib/apt@autozsys_kqk0hl 0B - 55.7M - rpool/ROOT/ubuntu_z6p9vy/var/lib/apt@autozsys_2ivctg 92K - 55.7M - rpool/ROOT/ubuntu_z6p9vy/var/lib/apt@autozsys_3f11n0 100K - 55.7M - rpool/ROOT/ubuntu_z6p9vy/var/lib/apt@autozsys_lv1ui9 124K - 51.4M - rpool/ROOT/ubuntu_z6p9vy/var/lib/dpkg@autozsys_ps1e80 0B - 32.3M - rpool/ROOT/ubuntu_z6p9vy/var/lib/dpkg@autozsys_kqk0hl 0B - 32.3M - rpool/ROOT/ubuntu_z6p9vy/var/lib/dpkg@autozsys_2ivctg 944K - 32.3M - rpool/ROOT/ubuntu_z6p9vy/var/lib/dpkg@autozsys_3f11n0 1.53M - 33.1M - rpool/ROOT/ubuntu_z6p9vy/var/lib/dpkg@autozsys_lv1ui9 1.44M - 32.6M - rpool/ROOT/ubuntu_z6p9vy/var/log@autozsys_ps1e80 80K - 1.80M - rpool/ROOT/ubuntu_z6p9vy/var/log@autozsys_kqk0hl 80K - 1.80M - rpool/ROOT/ubuntu_z6p9vy/var/log@autozsys_2ivctg 1.16M - 1.97M - rpool/ROOT/ubuntu_z6p9vy/var/log@autozsys_3f11n0 1.29M - 2.15M - rpool/ROOT/ubuntu_z6p9vy/var/log@autozsys_lv1ui9 2.43M - 3.40M - rpool/ROOT/ubuntu_z6p9vy/var/mail@autozsys_ps1e80 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/mail@autozsys_kqk0hl 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/mail@autozsys_2ivctg 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/mail@autozsys_3f11n0 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/mail@autozsys_lv1ui9 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/snap@autozsys_ps1e80 0B - 104K - rpool/ROOT/ubuntu_z6p9vy/var/snap@autozsys_kqk0hl 0B - 104K - rpool/ROOT/ubuntu_z6p9vy/var/snap@autozsys_2ivctg 0B - 112K - rpool/ROOT/ubuntu_z6p9vy/var/snap@autozsys_3f11n0 0B - 112K - rpool/ROOT/ubuntu_z6p9vy/var/snap@autozsys_lv1ui9 0B - 112K - rpool/ROOT/ubuntu_z6p9vy/var/spool@autozsys_ps1e80 0B - 112K - rpool/ROOT/ubuntu_z6p9vy/var/spool@autozsys_kqk0hl 0B - 112K - rpool/ROOT/ubuntu_z6p9vy/var/spool@autozsys_2ivctg 56K - 112K - rpool/ROOT/ubuntu_z6p9vy/var/spool@autozsys_3f11n0 0B - 112K - rpool/ROOT/ubuntu_z6p9vy/var/spool@autozsys_lv1ui9 0B - 112K - rpool/ROOT/ubuntu_z6p9vy/var/www@autozsys_ps1e80 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/www@autozsys_kqk0hl 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/www@autozsys_2ivctg 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/www@autozsys_3f11n0 0B - 96K - rpool/ROOT/ubuntu_z6p9vy/var/www@autozsys_lv1ui9 0B - 96K - rpool/USERDATA/jerry_0mgvki@autozsys_nt6t1g 148K - 1.69M - rpool/USERDATA/jerry_0mgvki@autozsys_ps1e80 0B - 1.74M - rpool/USERDATA/jerry_0mgvki@autozsys_kqk0hl 0B - 1.74M - rpool/USERDATA/jerry_0mgvki@autozsys_2ivctg 364K - 2.61M - rpool/USERDATA/jerry_0mgvki@autozsys_m38icf 13.5M - 39.6M - rpool/USERDATA/jerry_0mgvki@autozsys_x34i0j 11.0M - 77.5M - rpool/USERDATA/jerry_0mgvki@autozsys_h8dw72 1.29M - 82.0M - rpool/USERDATA/jerry_0mgvki@autozsys_3f11n0 928K - 82.3M - rpool/USERDATA/jerry_0mgvki@autozsys_lv1ui9 748K - 87.1M - rpool/USERDATA/jerry_0mgvki@autozsys_sgr37g 728K - 87.0M - rpool/USERDATA/jerry_0mgvki@autozsys_qopq6v 132K - 87.0M - rpool/USERDATA/root_0mgvki@autozsys_ps1e80 0B - 104K - rpool/USERDATA/root_0mgvki@autozsys_kqk0hl 0B - 104K - rpool/USERDATA/root_0mgvki@autozsys_2ivctg 0B - 104K - rpool/USERDATA/root_0mgvki@autozsys_3f11n0 0B - 104K - rpool/USERDATA/root_0mgvki@autozsys_lv1ui9 0B - 104K - jerry@jerry-Standard-PC-Q35-ICH9-2009:~$
rpool/USERDATA/jerry_0mgvki,
is snapshoted 11 times. Nine of those snapshots have different REFER values, so they must use different parameters for their snapshot command. Here is what I did to make and destroy a snapshot of my home account:
Notice that I did not have to exit /home/jerry in order to do the rollback of /home/jerry to recover the Documents folder. When I am running on BTRFS I usually sudo -i in a Konsole and mount the device BTRFS is running on to /mnt. So, while I have left /home/jerry I haven't really left the system. It is still running. IF I were to replace @ with a snapshot and/or @home with a snapshot, I'd have to umount /mnt, exit root to return to /home/jerry and reboot the system to make the snapshot the working system. That's easy to do, but not as convenient as ZFS.Code:sudo zfs snapshot rpool/USERDATA/jerry_0mgvki@SUNDAY04-26-20 zfs list -t snapshot (verify it is in the snapshot list) rm -rf /home/jerry/Documents (delete the Documents directory) vdir (verify Documents is no longer present) sudo zfs rollback rpool/USERDATA/jerry_0mgvki@SUNDAY04-26-20 vdir (verify Documents has been restored) sudo zfs destroy rpool/USERDATA/jerry_0mgvki@SUNDAY04-26-20 zfs list (verify that the snapshot has been destroyed)
Here are the properties of my /home/jerry subvolume:
There are about 70+ properties associated with my subvolume. I don't know how many of them are user tweakable. I know of only one property that is user setable in BTRFS; changing the r/w property of a snapshot.Code:jerry@jerry-Standard-PC-Q35-ICH9-2009:~$ zfs get all rpool/USERDATA/jerry_0mgvki NAME PROPERTY VALUE SOURCE rpool/USERDATA/jerry_0mgvki type filesystem - rpool/USERDATA/jerry_0mgvki creation Sun Apr 26 14:08 2020 - rpool/USERDATA/jerry_0mgvki used 126M - rpool/USERDATA/jerry_0mgvki available 22.2G - rpool/USERDATA/jerry_0mgvki referenced 87.0M - rpool/USERDATA/jerry_0mgvki compressratio 1.69x - rpool/USERDATA/jerry_0mgvki mounted yes - rpool/USERDATA/jerry_0mgvki quota none default rpool/USERDATA/jerry_0mgvki reservation none default rpool/USERDATA/jerry_0mgvki recordsize 128K default rpool/USERDATA/jerry_0mgvki mountpoint /home/jerry local rpool/USERDATA/jerry_0mgvki sharenfs off default rpool/USERDATA/jerry_0mgvki checksum on default rpool/USERDATA/jerry_0mgvki compression lz4 inherited from rpool rpool/USERDATA/jerry_0mgvki atime on default rpool/USERDATA/jerry_0mgvki devices on default rpool/USERDATA/jerry_0mgvki exec on default rpool/USERDATA/jerry_0mgvki setuid on default rpool/USERDATA/jerry_0mgvki readonly off default rpool/USERDATA/jerry_0mgvki zoned off default rpool/USERDATA/jerry_0mgvki snapdir hidden default rpool/USERDATA/jerry_0mgvki aclinherit restricted default rpool/USERDATA/jerry_0mgvki createtxg 152 - rpool/USERDATA/jerry_0mgvki canmount on local rpool/USERDATA/jerry_0mgvki xattr sa inherited from rpool rpool/USERDATA/jerry_0mgvki copies 1 default rpool/USERDATA/jerry_0mgvki version 5 - rpool/USERDATA/jerry_0mgvki utf8only on - rpool/USERDATA/jerry_0mgvki normalization formD - rpool/USERDATA/jerry_0mgvki casesensitivity sensitive - rpool/USERDATA/jerry_0mgvki vscan off default rpool/USERDATA/jerry_0mgvki nbmand off default rpool/USERDATA/jerry_0mgvki sharesmb off default rpool/USERDATA/jerry_0mgvki refquota none default rpool/USERDATA/jerry_0mgvki refreservation none default rpool/USERDATA/jerry_0mgvki guid 8843932201193722231 - rpool/USERDATA/jerry_0mgvki primarycache all default rpool/USERDATA/jerry_0mgvki secondarycache all default rpool/USERDATA/jerry_0mgvki usedbysnapshots 39.4M - rpool/USERDATA/jerry_0mgvki usedbydataset 87.0M - rpool/USERDATA/jerry_0mgvki usedbychildren 0B - rpool/USERDATA/jerry_0mgvki usedbyrefreservation 0B - rpool/USERDATA/jerry_0mgvki logbias latency default rpool/USERDATA/jerry_0mgvki objsetid 216 - rpool/USERDATA/jerry_0mgvki dedup off default rpool/USERDATA/jerry_0mgvki mlslabel none default rpool/USERDATA/jerry_0mgvki sync standard inherited from rpool rpool/USERDATA/jerry_0mgvki dnodesize auto inherited from rpool rpool/USERDATA/jerry_0mgvki refcompressratio 1.57x - rpool/USERDATA/jerry_0mgvki written 0 - rpool/USERDATA/jerry_0mgvki logicalused 202M - rpool/USERDATA/jerry_0mgvki logicalreferenced 131M - rpool/USERDATA/jerry_0mgvki volmode default default rpool/USERDATA/jerry_0mgvki filesystem_limit none default rpool/USERDATA/jerry_0mgvki snapshot_limit none default rpool/USERDATA/jerry_0mgvki filesystem_count none default rpool/USERDATA/jerry_0mgvki snapshot_count none default rpool/USERDATA/jerry_0mgvki snapdev hidden default rpool/USERDATA/jerry_0mgvki acltype posixacl inherited from rpool rpool/USERDATA/jerry_0mgvki context none default rpool/USERDATA/jerry_0mgvki fscontext none default rpool/USERDATA/jerry_0mgvki defcontext none default rpool/USERDATA/jerry_0mgvki rootcontext none default rpool/USERDATA/jerry_0mgvki relatime on inherited from rpool rpool/USERDATA/jerry_0mgvki redundant_metadata all default rpool/USERDATA/jerry_0mgvki overlay off default rpool/USERDATA/jerry_0mgvki encryption off default rpool/USERDATA/jerry_0mgvki keylocation none default rpool/USERDATA/jerry_0mgvki keyformat none default rpool/USERDATA/jerry_0mgvki pbkdf2iters 0 default rpool/USERDATA/jerry_0mgvki special_small_blocks 0 default rpool/USERDATA/jerry_0mgvki com.ubuntu.zsys:bootfs-datasets rpool/ROOT/ubuntu_z6p9vy local rpool/USERDATA/jerry_0mgvki com.ubuntu.zsys:last-used 1587951969 local jerry@jerry-Standard-PC-Q35-ICH9-2009:~$
So, as you can see, there is a lot to learn. I'm 78. I don't know if I have enough time left to learn it all, or even enough of it to be useful.
EDIT:
I forgot to add how ZFS properties of a pool are set:
zfs set someproperty=somevalue somepool
Setting properties in BTRFS is:
btrfs property set -ts /path/to/snapshot ro false
which changes a read only (ro) snapshot to read/write, using backward logic. There are only a handful of properties that can be set in BTRFS but the property shown is the only one I've ever used.Last edited by GreyGeek; Apr 27, 2020, 12:42 PM."A nation that is afraid to let its people judge the truth and falsehood in an open market is a nation that is afraid of its people.”
– John F. Kennedy, February 26, 1962.Comment
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I downloaded a fresh Kubuntu 20.04 ISO and created a VM in order to checked and see if it allowed using ZFS. It does not.
So, I will continue with Ubuntu 20.04"A nation that is afraid to let its people judge the truth and falsehood in an open market is a nation that is afraid of its people.”
– John F. Kennedy, February 26, 1962.Comment
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I did the same as you, to see the new Ubuntu and to try out ZFS and maybe learn how to use it. Before I do so, I'm going to look for a decent manual. But I'm happy with BTRFS so far--it made my clean install of Kubuntu 20.04 go quite smoothly, apart from errors I made. Thanks to all for the feedback.Comment
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I thought that perhaps I could reinstall UbuntuDDE and play with Deepin and ZFS at the same time. Alas, just like Kubunut, UbuntuDDE does not offer the "Advanced ..." button that leads to a ZFS installation. Both allow BTRFS, of course.
In order to run a BTRFS's check utility you have to shut down the <ROOT_FS>, i.e., shut down your computer and boot into a USB Live medium that has BTRFS installed. Just creating a USB Live stick won't cut it because BTRFS isn't installed by default, so BTRFS has to be selected during the hardware part of the installation routine. So, from a USB Live stick of Kubuntu you choose to install Kubuntu onto another USB stick, choosing BTRFS as the root filesystem. That gives you a USB Live stick of Kubuntu that runs on top of BTRFS and contains all the BTRFS utilities. THEN, the btrfs check utility can be run against the internal drive containing the BTRFS system volumes @ and @home which, of course, are not running. I've been using BTRFS for 4 1/2 years, and I have never needed to do a check on my system because it has never given me a single problem.
With ZFS a single disk or a striped set does not have error correction, only error detection. It would be ideal of one could merely install zfs-intramfs to add ZFS utilities to the running system, but one has to follow the same method outlined for the BTRFS USB stick. Also, ZFS doesn't have a "check" utility or a fsck utility, but it does have scrub. While ZFS is performing a scrub on your pool, it is checking every block in the storage pool against its known checksum. Scrubbing ZFS storage pools is not something that happens automatically. You need to do it manually, and it's highly recommended that you do it on a regularly scheduled interval, depending on the quality of your hardware. Once a month for good hardware, once a week for consumer grade hardware. Unlike BTRFS, the pool you are checking does NOT need to be taken offline.
Being able to scrub while continuing to use the filesystem gives ZFS the advantage in repairing data errors.
Using the mkusb utility (added via their PPA (make sure you also install usb-pack-efi too) , one can create a persistent USB Live stick with both BTRFS and ZFS installed, from which those commands can be run against the non-running system that needs to be checked. Install zfs-intramfs to use OpenZFS (not zfs-fuse) and bttrfs-progs to utilize BTRFS. With those two installed it doesn't matter what file system the persistent USB Live stick is using. In fact, a persistent stick should contain the ntfs file system as the persistent storage part in order for it to be readable by all three major OSs."A nation that is afraid to let its people judge the truth and falsehood in an open market is a nation that is afraid of its people.”
– John F. Kennedy, February 26, 1962.Comment
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ZFS v BTRFS cont
One of the features of BTRFS is the ability to mount the <ROOT_FS>, usually to /mnt, and then navigate through any snapshots stored under /mnt/snapshots using Dolphin or mc, and copy any file found inside that snapshot to any subdirectory in your running system. BTRFS snapshots are truly independent. I can delete any snapshot regardless of when it was created or if any were created before or after it. I can also rollback to any snapshot without affecting the other snapshots, aside from the normal CoW operations.
One can browse a ZFS snapshot and pull files from it, even though it is read only, although one doesn't have to mount it because it is part of the running system. Rolling back to a specific snapshot destroys any snapshots made before it. A clone created from a snapshot is rw. If one wants to destroy a snapshot they must first destroy any clones made from that snapshot. Using the "-r" flag will do that automatically.
Something that ZFS has and BTRFS doesn't (to the best of my knowlege) is Virtual Devices, called VDEV's. ZFS uses adaptive read caching, called ARC, which is RAM intensive. All but 1 Gb of RAM is usually given to ARC. There is also a "Level 2 adaptive read cache", called L2ARV, or just cache. Because ZFS reads and writes aggressively to storage devices, it can eat up USB sticks which do not have write leveling pretty fast. To minimize that a cache is used. You can set up the cache to minimize the USB wear by usingZFS Virtual Devices (ZFS VDEVs)
A VDEV is a meta-device that can represent one or more devices. ZFS supports 7 different types of VDEV:
- File - a pre-allocated file
- Physical Drive (HDD, SDD, PCIe NVME, etc)
- Mirror - a standard RAID1 mirror
- ZFS software raidz1, raidz2, raidz3 'distributed' parity based RAID
- Hot Spare - hot spare for ZFS software raid.
- Cache - a device for level 2 adaptive read cache (ZFS L2ARC)
- Log - ZFS Intent Log (ZFS ZIL)
VDEVS are dynamically striped by ZFS. A device can be added to a VDEV, but cannot be removed from it.
zfs set secondarycache=metadata pool
where secondarycache is a property, metadata is a value, and pool is the pool the property is being applied to. Create cache in pool and it will minimize SSD or USB unlevel wearing. Just use
zpool add -f pool cache /dev/disk/by-id/usb1id /dev/disk/by-id/usb2id /dev/disk/by-id/usb3id ... /dev/disk/by-id/usbnid
BTRFS does not have virtual devices nor "secondarycache" settings. It wouldn't be a good idea to install it on a group of USB sticks in order to test out various RAID configurations, unless you don't mind if they get worn out quickly.
At this point I began re-evaluating my plan to explore ZFS. Most of its vaunted reliability is lost when used on a typical single drive laptop or desktop with 16GB or less of non ECC memory. On a single drive it will detect errors but not correct them. You'll need to run scrub to do that. Run it with 4 or 8 Gb of memory and the adaptive read cache isn't as quick, and it leaves less of memory for your applications to run in. 16, or better yet, 64 Gb of ECC memory is best to use in order to make ZFS fast and still allow enough memory for your applications to run fast as well. 64Gb of good ECC memory is selling for around $200 at Amazon.
Snapshotting and rollbacks are quicker in ZFS, but even doing it manually I take less than a minute to snapshot, less than 2 minutes to do an incremental backup to my 2nd SSD or my spinner, and rollbacks aren't much slower. Plus, my snapshots are outside of @ and @home. To lose them my HD would have to have a hardware failure. Even ZFS can't prevent that on non-commercial systems.
All in all, IMO, BTRFS is the best filesystem to use on my laptop, even though I have an Nvidia GPU and an i7 CPU with 16GB of RAM and three storage devices. One is a Toshiba spinner on its last legs. The other two are Samsung 860 EVO 500Gb SSD's. Their statistics are:
Power on time 282 days 20 hours 90 days 4 hours
Est Time Remaining > 1000 days > 1000 days
Lifetime Writes 10.54 TB 435.71 GB
I'm averaging about 12 hours a day on this laptop, usually between 12 noon and 12 midnight. BTRFS has been gentle to my SSDs. I think I'll keep it that way.
Signing off of my ZFS experiment, which as triggered by UbuntuDDE. UDDE is interesting but nowhere near Kubuntu in power and ease of use. Running UDDE on ZFS would offer nothing new but a pretty hummingbird wallpaper, which I'll probably download and use.Last edited by GreyGeek; Apr 27, 2020, 02:42 PM."A nation that is afraid to let its people judge the truth and falsehood in an open market is a nation that is afraid of its people.”
– John F. Kennedy, February 26, 1962.Comment
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