On Tue, Jan 5, 2021 at 9:41 AM Richard Brown <rbrown@suse.de> wrote:
On Mon, 2020-12-21 at 19:06 +0100, Dario Faggioli wrote:
Hello,
I've finally had the chance to put in a VM an instance of MicroOS Desktop with the new partition layout and. IMO, the fact that it has /var in a (nocow) subvolume is really a big improvement, so thanks Richard for that!
We have /home in a subvolume too, which is also great, and it as well has the nocow flag set. I know this mostly come from a conversation we had on #microos-desktop on IRC but thinking more about that, and discussing this with some users, I wonder whether it is really the best choice.
I mean, it sure is ok for /var, but for /home, using nocow means that we give up on some of the nicer BTRFS features, especially for home folders, wouldn't it?
That might be especially true for MicroOS Desktop. E.g., think at being able to compress (if not the entire home directories or the entire subvolume) the user installed flatpaks (and using that as an argument "against" those that are still complaining that <Ah, but flatpaks takes a lot of space on disk!>> :-D).
So, are there reasons why it's really preferable to keep the /home subvolume as nocow and I'm missing them? Or shall we switch it to cow?
There's one, which is the main reason I did it in the first place
GNOME Boxes (IMHO the best virtualisation tool) or virt-manager User Sessions puts qcow2 VM images in /home
libvirt, since 6.7.0, automatically provisions storage pools on btrfs with nodatacow by default. This obviates the need to have /home as nodatacow by default.
And in KDE there's database-like tools like akondi (sp?) with its datastore in /home
I don't think Akonadi does anything special when initializing its datastore on Btrfs, though I personally haven't worried about it either...
Also, while there, shall we evaluate adding other flags by default (i.e., things like autodefrag, or even compression itself)?
This is an interesting idea - but I'd rather we consider what makes sense for all of openSUSE there. I dont see MicroOS Desktop really bringing in unique requirements when it comes to autodefrag or compression.
There's been some discussion in Fedora about autodefrag: https://pagure.io/fedora-btrfs/project/issue/16 The issue right now is that the autodetection of applicability of autodefrag isn't reliable enough. :(
E.g., AFAIUI, on Fedora, while not doing that right now, they're considering doing something like that, e.g.:
I'm expecting Fedora to implement it. The Change has been submitted for review, and I don't expect it to be controversial. -- 真実はいつも一つ！/ Always, there's only one truth!