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Re: RE:Re: RE:How to decide mode and journal size?



Hi,

On Wed, Apr 03, 2002 at 02:40:07PM +0200, Ralf Hildebrandt wrote:
> On Wed, Apr 03, 2002 at 02:23:01PM +0200, Diego SANTA CRUZ wrote:
 
> > How is this affected if there are several ext3 filesystems mounted? Can
> > all journals be resident in memory at a time?
> 
> The journal is NOT in memory. 

That's only partially correct.  The whole point of the journal is to
hold recent write requests before those writes get written back to
their permanent backing store locations.  As a result, all of the
journal writes for a single transaction *are* pinned in memory until
the transaction commits --- only after the commit can we start doing
the permanent writeback.  So, part of the journal will most definitely
be in memory during fs activity.

The amount of memory pinned is related to the transaction size,
though, and not directly to the whole journal size --- we don't ever
keep the entire journal in memory.

Cheers,
 Stephen





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