On 24/08/17 00:03, Adam Borowski wrote:
> Hi!
> I'd like to recommend another improvement: let's make the installer default
> to noatime for fstab it creates.
>
> In the past, atime updates used to ruin performance. Thanks to work by Ted
> Ts'o and others, that penalty has been greatly reduced (but not eliminated)
> by two options:
> * relatime (on by default): atime is not updated unless atime<=mtime or
> atime<NOW-24h
> * lazytime (off by default): atime and mtime updates are postponed by up to
> 30 minutes, unless there's memory pressure or the inode has to be written
> for another reason
>
> But alas, there are more considerations than just performance:
> * atime is really nasty for any CoW filesystems (btrfs, zfs, lvm snapshots,
> qcow2 snapshots, deduped thin storage, etc). For a /usr-y mix of files,
> it costs around 5% of disk space per snapshot. relatime offers no help as
> its threshold (24h) just happens to match the most popular snapshot and
> cronjob frequency (once per day). Even worse, it can make _reading_
> things result in ENOSPC!
> * atime murders media with sharply limited write endurance, such as SD
> cards. For this reason, every SoC pre-made image I've seen ships with
> noatime.
>
> And what do we get in return?
> * the "vote" field in popcon. This somewhat benefits the distribution (lets
> us spot low-use packages installed by default, such as xterm (53.60% inst,
> 6.67% vote) or tcpd (95.20% inst, 9.85% vote)) but gives no gain to
> individual users.
> * some rare forensic uses
> * new mail notification on login
>
> The last thing has recentlish (POSIX-2008) gained a solution: mail readers
> can be patched to manually calls futimens(f, {UTIME_NOW, UTIME_OMIT});
> stretch/ascii already sports mutt patched this way -- not sure what other
> mail clients are likely to be used by local users thus worthy of patching.
> Sample patch:
> https://github.com/neomutt/neomutt/commit/816095bfdb72caafd8845e8fb28cbc8c6afc114f
> Because of stretch's freeze, I did not manage to write+push upstream patches
> for any client other than mutt, I guess it's time to resume.
>
> Obviously, an admin who thinks he actually has an use for atime is free to
> edit fstab.
>
> So, what would you folks say about defaulting to noatime?
>
>
> Meow!
I always set noatime to 'off' when I do an install.
I agree it should be the default, anybody who wants atime to be 'on'
knows what they are doing and why.
I always use non-graphical expert install, I would expect the noatime
box to be ticked for me by the time I get to that screen.
I always install and use xterm.
DaveT
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Re: [DNG] noatime by default
