Re: noatime on ufs2

Olivier Certner <olce_at_freebsd.org> wrote on
Date: Wed, 10 Jan 2024 10:01:48 UTC :

> What I'm saying is that, based on others' input so far, my own (long, even if not as long as yours) experience and some late reflection, is that "noatime" should be the default (everywhere, all mounts and all FSes), and that working on "relatime" won't make any real difference for most users (IOW, I think that developing "relatime" is a bad idea *in general*). And I think this is a sufficiently reasonable conclusion that anyone with the same inputs would conclude the same. So, if it's not the case, I would be interested in knowing why, ideally.

I never use atime, always noatime, for UFS. That said, I'd never propose
changing the long standing defaults for commands and calls. I'd avoid:

A) Having natives & required file systems with mismatching defaults.
    ("required" is for spanning efi/msdosfs partitions if the atime/noatime
    makes a distinction there. So not just UFS/FFS and ZFS.)

B) Having files systems that are not OS specific have unusual defaults
    compared to those other OS's when there is documented uniformity.
    (openzfs being such an example file system.)

C) Having defaults unlike most other closely related operating systems
    that support the file system when there is generally documented
    uniformity. (No claim to have checked on the uniformity generally.)
    (Other BSDs, Unix, Linux, . . .)

D) Having defaults for non-native files systems that are different than
    the native contexts for the file system have when they have uniformity.
    (So, for example, linux ext4 use would get linux etx4 default behavior
     for atime vs. noatime if such is basically uniform across most
     linux's.)

Note: I've worded the above as if things are always per file system.
Command default that apply across file systems that have the feature
of allowing stored atime are also relevant. But the wording gets messy
if expanded in each relevant place above.

Picking openzfs as an example of documented uniformity . . .

https://openzfs.github.io/openzfs-docs/man/master/7/zfsprops.7.html documents:

QUOTE
atime=on|offControls whether the access time for files is updated when they are read. Turning this property off avoids producing write traffic when reading files and can result in significant performance gains, though it might confuse mailers and other similar utilities. The values on and off are equivalent to the atime and noatime mount options. The default value is on.
END QUOTE

Unless openzfs manges to decide to change that default across OSs,
in my view FreeBSD should have it be left as documented for its use
of openzfs. Given that, having FreeBSD UFS/FFS be the other way
would be problematical in my view, even ignoring defaults for
non-FreeBSD that support UFS/FFS use.

In my view , the burden to make things work relative such defaults
is not worth the consequences of making a bunch of new distinctions
in a long standing subject area.

===
Mark Millard
marklmi at yahoo.com