[Lustre-discuss] lfs find and file size.

[James Beal]

On 17 Feb 2012, at 17:45, Nathan Dauchy wrote:

> James,
> 
> Depending on how often you need the information updated, and how
> perfectly accurate it has to be, you may find that just using normal
> "find" on a snapshot of the MDT is more efficient.  (IIRC that
> size-on-mds is relatively close these days.)  If you have your MDT on
> LVM for making backups (for example), you could also periodically run
> your find on the same snapshot.

We generally do have the mdt on LVM however I am adverse to taking snapshots of it as the performance hit while you have a snapshot is pretty severe. And we don't back any of our lustre systems up.

> With your "lfs find" approach, I think you will have to decide if you
> want to trust the size-on-mds anyway or query the OSTs which will slow
> things down a lot.  There is more than one way to do it.

Given that we run the scan about once a month, If the size-on-mds was relatively up to date then I would love to use it. On our general purpose filesystems running a scan using real stats is not feasible.  However I don't have a clue how to get at the size on mdt, If anyone would point me at some documentation then that would be grand.

> 
> -Nathan
> 
> PS: I love the color-coded bar graph approach... very informative in a
> compact display!

Just in case it wasn't clear agedu is written by Simon Tatham who is also know for PuTTY, I have sent him a few emails and he responds very quickly and he seems a very bright fellow.




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