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Comment by mg | Hacker News Reader

Did they read and write all the data a filesystem handles?

Off the top of my head, the typical filesystem stores:

    - content
    - creation time
    - modification time
    - last access time
    - read/write/execute permissions
    - owner
    - group
    - position in the dir hirarchy

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Turning off `atime` is about the first thing you do when you care about filesystem performance.

That advice is mostly obsolete, lazytime has been a thing for years.

lazytime isn't default though is it? So changing fs time options is still useful advice.

Well, same point: keeping track of atime is way too expensive and barely useful.

Lazytime is a pretty good hack, but it doesn't survive a crash, does it?

Few things need atime at all, even fewer things need synchronous durability guarantees for atime (I'm not aware of any). So writing it out in the background (either when evicting disk cache or after 24h) while keeping the in-memory representation up to date is good enough for most use-cases.

I agree. My point was that many of the items mentioned in https://news.ycombinator.com/item?id=34387703 were pointless / unnecessary.

Did this for a mdadm raid system using btrfs and the difference was very noticeable on a CI build machine.

Maybe not, but if all small files in a directory have the same structure, permissions, owner and same parent directory, and you don't care about x-times, you might as well use this context.

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