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Re: selectively disabling atime updates?



Thor Lancelot Simon <tls%panix.com@localhost> writes:

> On Mon, Jun 11, 2012 at 05:52:27PM +0200, Edgar Fu? wrote:
>> > Yes, but I have to question whether and why it would improve performance
>> > in this case.  The stream of atime updates is still happening on the
>> > underlying filesystem, and that is still where you will be doing almost
>> > all of your reads from.
>>
>> My intent was to mount the snapshot ro,noatime and operate on that.
>> Am I again missing something stupid?

You should only need ro; it doesn't make sense to talk about atime
updates or not when you aren't writing to the underlying block device.

> Hm.  No, I don't think so.  I wonder -- will the snapshot management code
> cause the resulting snapshot to be in a consistent state so access through
> the filesystem is safe?

I would say that it should or it's a bug; it seems the whole point of
snapshots is to get a consistent view of a filesystem.
Given that the normal use case seems to be things like
snapshot/dump/drop-snapshot, I would think that if it were buggy there's
a decent chance there would have been complaints by now.

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