[Lustre-discuss] large ost and fsck

Brian J. Murrell Brian.Murrell at Sun.COM
Tue Oct 28 05:16:04 PDT 2008

On Tue, 2008-10-21 at 12:00 -0400, Kossey, Robert wrote:
> Can you be more specific about the 8TB limit?  Is it correct that this 
> is an 8TB base 2 (8796GB base 10) limit?

Probably it would be useful here and in our documentation to observe and
be explicit that we are observing the IEC standard for base 2 and base
10 naming.  http://www.iec.ch/zone/si/si_bytes.htm

This is not to imply that our documentation is currently adhering to one
or the other (or consistent) but that clarification and consistency
would be a good enhancement.

So the question is is the limit 8TiB or 8TB?

> Does this limit apply to the raw device size or formatted Lustre OST 
> size?

I think it's the raw disk size because this limit is a limit imposed by
the ext3 filesystem.  According to
http://en.wikipedia.org/wiki/Ext3#Size_limits the limit is indeed 8TiB
and not 8TB.

> Using RHEL5U1, we have created an OST on a 9.001 TB

TiB or TB?  Respectively those amount to

9,896,704,161,611.776 and 9,001,000,000,000 bytes.

When those are converted to TiB they are are:

9.001 and 8.18636 TiB (respectively) which are both more than 8TiB.

> Is this 
> OST OK to use, or would we have receive an error message if it was not OK?

I'm not sure what the consequences of using an OST > 8TiB are to be


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