PC Engines apu2 experiences

dem

@vollans Thank you for the writeup. It's good to know this works.

Now please try pool checkpointing and let us know how it goes. You'll need to boot from the installer and use the rescue image to recover.

From the zpool Manual Page:

Pool checkpoint

Before starting critical procedures that include destructive actions (e.g zfs destroy ), an administrator can checkpoint the pool's state and in the case of a mistake or failure, rewind the entire pool back to the checkpoint. Otherwise, the checkpoint can be discarded when the procedure has completed successfully.

A pool checkpoint can be thought of as a pool-wide snapshot and should be used with care as it contains every part of the pool's state, from properties to vdev configuration. Thus, while a pool has a checkpoint certain operations are not allowed. Specifically, vdev removal/attach/detach, mirror splitting, and changing the pool's guid. Adding a new vdev is supported but in the case of a rewind it will have to be added again. Finally, users of this feature should keep in mind that scrubs in a pool that has a checkpoint do not repair checkpointed data.

To create a checkpoint for a pool:

# zpool checkpoint pool

To later rewind to its checkpointed state, you need to first export it and then rewind it during import:

# zpool export pool
# zpool import --rewind-to-checkpoint pool

To discard the checkpoint from a pool:

# zpool checkpoint -d pool

Vollans

@dem I'll give that a go when I've got some spare time next week or when an updated 2.5 comes out.

dem

@vollans I did a quick test in a virtual machine to figure out what the commands would be. This appears to work:

On a running 2.4.5-p1 system:

zpool checkpoint zroot

Booted from the 2.5.0 installer and in the Rescue Shell:

zpool import -f -N --rewind-to-checkpoint zroot
zpool export zroot
poweroff

logan5247

@vollans Thanks for this write up! I am installed on UFS but may go back and switch to ZFS now. I'm a Linux guy, so ZFS has always been out of my wheelhouse.

When I do the initial setup and pfSense is working, do I:

Perform a snapshot then and leave it around for years and years? Is this safe? I'm thinking like a VM snapshot where you don't want to have a snapshot hang around for long periods of time.
Only perform snapshots before an upgrade, do the upgrade, then remove the snapshot after it's working?

Thanks again!

VAMike

@logan5247 said in PC Engines apu2 experiences:

@vollans Thanks for this write up! I am installed on UFS but may go back and switch to ZFS now. I'm a Linux guy, so ZFS has always been out of my wheelhouse.

This is an issue mainly because UFS in pfsense performs recovery so incredibly badly. I don't fully understand why something as heavy as ZFS seems to be the only solution.

Vollans

@logan5247 I don’t see any inherent dangers in leaving the snapshot hanging around, unless you are really tight for space. Snapshots only record changed files, so it’s not a huge thing. Personally, I use it for a couple of reasons.

Fully installed with patches base OS before any fiddling - that way if you screw up you can roll back and undo your “magic” that was more Weasley than Granger.
Snapshot once fully tweaked and working, so you’ve got a known working system to roll back to
Just before a major upgrade

Here’s my snapshot catalogue:

NAME                              USED  AVAIL  REFER  MOUNTPOINT
zroot                            2.90G  9.21G    88K  /zroot
zroot@210219                         0      -    88K  -
zroot@2-4-5p1-base                   0      -    88K  -
zroot@2-4-5-p1                       0      -    88K  -
zroot/ROOT                       2.14G  9.21G    88K  none
zroot/ROOT@210219                    0      -    88K  -
zroot/ROOT@2-4-5p1-base              0      -    88K  -
zroot/ROOT@2-4-5-p1                  0      -    88K  -
zroot/ROOT/default               2.14G  9.21G  1.84G  /
zroot/ROOT/default@210219         146M      -  1.14G  -
zroot/ROOT/default@2-4-5p1-base  36.3M      -  1.43G  -
zroot/ROOT/default@2-4-5-p1      36.5M      -  1.43G  -
zroot/tmp                         512K  9.21G   512K  /tmp
zroot/var                         776M  9.21G   396M  /var
zroot/var@210219                  183M      -   527M  -
zroot/var@2-4-5p1-base           52.1M      -   409M  -
zroot/var@2-4-5-p1               61.5M      -   434M  -

The space used as it goes along is tiny. The upgrade to 2.5 that I ended up rolling back from only used about 900MB IIRC.

kevindd992002

Without doing manual snapshots, is there an advantage of using ZFS over the old UFS? I am on ZFS on a single SSD and I forgot what its advantage is when I posted here a few years ago.

Vollans

@kevindd992002 Better resilience if you have a crash. UFS has a horrid habit of collapsing in an unrecoverable heap, ZFS is far more likely to recover gracefully.

Qinn

@kevindd992002 said in PC Engines apu2 experiences:

Without doing manual snapshots, is there an advantage of using ZFS over the old UFS? I am on ZFS on a single SSD and I forgot what its advantage is when I posted here a few years ago.

....of course RAID with ZFS gives more redundancy, best is more disks using RAID. As the problem with a single disk and "copies" is the same as creating an mdadm raid-1 using two partitions of the same disk: you have data redundancy, but not disk redundancy, as disk failure will cause the loss of both data sets.

Comparing UFS with ZFS, well ZFS, like btrfs, is copy-on-write, so power surges are never a problem and ZFS requires a system with ECC memory (APU2 has this), otherwise you're still not 100% safeguarded against bit errors.

logan5247

@vollans Sorry to keep asking questions.

) If I snapshot zroot do I need to snapshot zroot/ROOT and zroot/ROOT/default? Does zroot not include everything else?

Let's say I did a snapshot, made a change, and successfully rolled back:

zfs rollback zroot/var@20210308
zfs rollback zroot/ROOT/default@20210308
zfs rollback zroot/ROOT@20210308
zfs rollback zroot@20210308
shutdown -r now

And now my zfs list looks like this (after the rollback):

NAME                          USED  AVAIL  REFER  MOUNTPOINT
zroot                         674M  12.4G    96K  /zroot
zroot@20210308                   0      -    96K  -
zroot/ROOT                    665M  12.4G    96K  none
zroot/ROOT@20210308              0      -    96K  -
zroot/ROOT/default            665M  12.4G   665M  /
zroot/ROOT/default@20210308   388K      -   665M  -
zroot/tmp                     144K  12.4G   144K  /tmp
zroot/var                    7.02M  12.4G  6.62M  /var
zroot/var@20210308            400K      -  6.62M  -

How do I know what set of filesystems I'm running on? Is there something like an "active" marker in zfs list?

VAMike

@logan5247 this really should get its own zfs thread, it has nothing to do with the apu2

Vollans

@vamike I agree, but quickly in summary, you're always running the one without the @ sign - that's the current live version. You can see that the size of the "backup" of zroot is nothing. The size of zroot/ROOT/default's backup is bigger. zroot doesn't include the other, effectively, "partitions".

Qinn

@dem said in PC Engines apu2 experiences:

@vollans I did a quick test in a virtual machine to figure out what the commands would be. This appears to work:

On a running 2.4.5-p1 system:
zpool checkpoint zroot
Booted from the 2.5.0 installer and in the Rescue Shell:
zpool import -f -N --rewind-to-checkpoint zroot
zpool export zroot
poweroff

I would like to know how you booted from the 2.5.0 installer using a virtual pfsense machine and got to the Rescue Shell?

dem

@qinn In VirtualBox I put the file pfSense-CE-2.5.0-RELEASE-amd64.iso in the virtual optical drive and booted to this screen, where I selected Rescue Shell:

Qinn

@dem Thanks for the quick reply, I understand that.
What I would like to know is how you get to the Virtual pfSense from here as the virtual pfsense machine is not running and access the checkpoint you made?

Btw I am using VM workstation!

dem

@qinn Sorry I wasn't clear: I put the installer image into the virtual optical drive of the same virtual pfSense instance that I checkpointed, so the installer has access to the same virtual disk and can locate the checkpointed zroot pool.

Edited to add: My goal was to simulate booting an apu2 from the memstick image in order to rewind a checkpoint, but I don't have a spare apu2 to test with. If I actually ran pfSense in a virtual machine I would use virtual machine snapshots before any upgrade.

VAMike

@qinn I never would have guessed this was somehow specific to the apu2

dem

@vamike It's not, but @vollans rolled back an upgrade of his apu2 using ZFS and that sparked interest in using ZFS to recover from a failed upgrade.

VAMike

@dem so he should start another thread so that people actually interested in apu2 experiences can find those without digging through unrelated zfs support questions

Vollans

@vamike I agreed it wasn't relevant here 2 days ago, and stopped responding.