Journal questions

Andreas Dilger adilger at
Thu Mar 6 06:03:11 UTC 2008

On Mar 05, 2008  19:54 -0500, John Nelson wrote:
> 1. Will there be performance lose with a smaller journal say 32MB instead 
> of 128MB?

Depends on how high an IO/metadata rate you have.  If you are just doing
light desktop IO it won't make any difference.

> 2. Is there a way to see free space left in the journal or is it cleared at 
> each mount?

The journal is a circular buffer, so this is hard to determine exactly.

> 3. Is journal_data_ordered atomic like reiser4 where either a transaction 
> will happen or it wont happen?

I'm not sure what you mean - there is data=journal and data=ordered
mode.  data=journal means all data and metadata changes are atomic.
data=ordered (the default) means that data is written to disk before
metadata so if there is a crash that you don't get garbage in your

Cheers, Andreas
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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