Re: RFC: Exporting NOCMTIME to userspace

[Andi Kleen]

> While this might solve the performance aspect of the problem, it will
> only migitate the reliability aspect with NANDs, since the inodes will
> eventually be flushed anyway (thus causing irreversible wear).

As long as you don't run out of memory it will happen very rarely.
Completely elimintating inode writes is not a good goal imho.

Iff you don't want inodes at all then perhaps consider using a LVM volume or similar 
instead of a file system.

> Also, a tunable like you're suggesting would affect all files on a
> single filesystem, instead of just a subset of files. Having an option
> to "disable" m/ctime updates per file would be optimal in our case,
> since we're talking about several years of runtime with the use case.
> There are other issues with rrdtool which make this hard, but those are
> all solvable without kernel modifications.

Yes, but the nice thing is that the semantics are the same, so unless
you crash you won't really notice.

-Andi
-- 
ak@xxxxxxxxxxxxxxx -- Speaking for myself only.
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