[Lustre-discuss] Unbalanced OST--for discussion purposes

[Brian J. Murrell]

On Tue, 2010-03-02 at 15:45 -0500, Ms. Megan Larko wrote: 
> Hi,

Hi,

> I logged directly into the OSS (OSS4) and just ran a df (along with a
> periodic check of the log files).  I last looked about two weeks ago
> (I know it was after 17 Feb).

Is the implication that at this point the OSTs were more or less well
balanced?

> Anyway, the OST0007 is more full than
> any of the other OSTs.  The default lustre stripe (I believe that is
> set to 1) is used.    Can just one file shift the size used of one OST
> that significantly?

Sure.  As an example, if one had a 1KiB file on that OST, called, let's
say, "1K_file.dat" and one did:

$ dd if=/dev/zero of=1K_file.dat bs=1G count=1024

that would overwrite the 1KiB file on that OST with a 1TiB file.
Recognizing of course that that would be 1TiB in a single object on an
OST.

> What other reasonable explanation for a
> difference on one OST in comparison with the others?

Any kind of variation on the above.

> Could this cause
> a lustre performance hit at this point?

Not really.

b.

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