Re: [PLUG] RAID-1 mdadm vs. Mobo H/W

I avoid hardware RAID like the plague (or maybe avoid it like COVID-19 to be more contemporary). A new MoBo, or possibly a new MoBo firmware revision, could make your filesystems indistinguishable from a random array of bytes. I know of one case where the MoBo died on a PC that was using hardware RAID, and the MoBo was too old to buy a replacement. It was bad news for the filesystems. Admittedly that was some years ago, and perhaps things are different these days, but I would not personally go anywhere near MoBo RAID.

Instead of mirroring /, I treat it as a disposable file system. Any system I configure has a / and another partition of equal size mounted as /spare. For anything risky, I clone / to /spare and then do the action on /spare. /etc/fstab on the original /spare of course has / and /spare swapped. So, for example, my twice-a-year, or once every two years, Ubuntu upgrades on machines that I support with Ubuntu installed are (to avoid confusion, assume originally / is on partition A and /spare is on partition B):

While booted on A:

Clone A to B
Edit /etc/fstab on B to swap the / and /spare partitions
update-grub
Edit /boot/grub/boot.cfg on A to fix the UUIDs below the entries made by os-prober and save the file
Save the buffer (still open in emacs) as /spare/boot/grub/grub.cfg
Edit the UUIDs and partitions so that the file is a correct /boot/grub/grub.cfg when booted on B and save the file
Boot B

While booted on B:

Upgrade from 19.10 to 20.04 (or 18.04 to 20.04 depending on the system)
If the upgrade fails at any point, just reboot the machine – partition A and the bootloader are untouched
If the upgrade is successful, the last step in the upgrade process is to update the bootloader and reboot. If the risky procedure is something else, on successful completion, manually update the bootloader.
Reboot – by default, it should boot into B, and if anything is wrong with it, it's simple to discard B and revert to an untouched A – worst case, you have to boot with a live USB to reinstall the bootloader.

Regards

– Bhaskar

On Fri, Jul 17, 2020 at 9:21 AM Adam Schaible via plug <plug@lists.phillylinux.org> wrote:

On Fri, Jul 17, 2020, at 01:31, Rich Mingin (PLUG) wrote:
once you integrate [ZFS] snapshots into your workflow

Because it's *buntu, there's no workflow to integrate into, instead they just set it for you by default. This is typical *buntu style, the relative merits and demerits of which are best discussed elsewhere (JP has some installs to do after all), but here's what it looks like on my lab box:

schibes@ubuntu20-zfs:~$ sudo apt update && sudo apt -y install nmap
[sudo] password for schibes:
Hit:1 http://us.archive.ubuntu.com/ubuntu focal InRelease
...
...
Get:5 http://us.archive.ubuntu.com/ubuntu focal/universe amd64 nmap amd64 7.80+dfsg1-2build1 [1,662 kB]
Fetched 5,553 kB in 0s (13.2 MB/s)
Requesting to save current system state
Successfully saved as "autozsys_fd790r"
...
...
Setting up nmap (7.80+dfsg1-2build1) ...
Processing triggers for man-db (2.9.1-1) ...
Processing triggers for libc-bin (2.31-0ubuntu9) ...
ZSys is adding automatic system snapshot to GRUB menu
schibes@ubuntu20-zfs:~$

Happy trails,
--
Adam Schaible
plug@schibes.com

On Fri, Jul 17, 2020, at 01:31, Rich Mingin (PLUG) wrote:
Having been using ZFS for quite some time on FreeBSD, I'll just note that the features are no joke, and once you integrate snapshots into your workflow, you won't want to go back. The data integrity protection is very serious as well.

On Fri, Jul 17, 2020 at 12:57 AM Adam Schaible via plug <plug@lists.phillylinux.org> wrote:
On Thu, Jul 16, 2020, at 21:21, JP Vossen via plug wrote:
> [mdadm vs. HW raid comparison]
>
> Am I failing to consider anything? Any thoughts?
>

Since Mint is (technically) a *buntu distro, you also have a third option, ZFS on Linux aka ZoL:

https://forums.linuxmint.com/viewtopic.php?t=306210

Single drive installation is basically brainless, however to boot from a mirrored root pool (RAID 1 equivalent) you do still have to jump through some hoops:

https://openzfs.github.io/openzfs-docs/Getting Started/Ubuntu/Ubuntu 20.04 Root on ZFS.html

Benchmarks show that ZoL has slower read/write performance and uses more RAM than mdadm but it claims more "features" (snapshot backups, file compression, "self healing" checksums for data integrity).

Since you already have a lot of experience with mdadm you'll probably want to stick with that, just letting you know ZoL exists and seems to be (slowly) gaining popularity :-)

Good luck with your installs,

--
Adam Schaible
plug@schibes.com
___________________________________________________________________________
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___________________________________________________________________________
Philadelphia Linux Users Group -- http://www.phillylinux.org
Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce
General Discussion -- http://lists.phillylinux.org/mailman/listinfo/plug