On Sun, Aug 05, 2007 at 09:28:05AM +0200, Ingo Molnar wrote:

* Alan Cox [off-list ref] wrote:

quoted

quoted

 Can you give examples of backup solutions that rely on atime being 
updated? I can understand backup tools using mtime/ctime for 
incremental backups (like tar + Amanda, etc), but I'm having trouble 
figuring out why someone would want to use atime for that.

HSM is the usual one, and to a large extent probably why Unix 
originally had atime. Basically migrating less used files away so as 
to keep the system disks tidy.

atime is used as a _hint_, at most and HSM sure works just fine on an 
atime-incapable filesystem too. So it's the same deal as "add user_xattr 
mount option to the filesystem to make Beagle index faster". It's now: 
"if you use HSM storage add the atime mount option to make it slightly 
more intelligent. Expect huge IO slowdowns though."

The only remotely valid compatibility argument would be Mutt - but even 
that handles it just fine. (we broke way more software via noexec)

I find it pretty normal to use tmpreaper to clear out unused files from
certain types of semi-temporary directory structures. Those files are
often only ever read. They'd start randomly disappearing while in use.

But then again, maybe I'm the only guy on the planet who uses tmpreaper.

-- 

 / jakob

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