Re: ext3 filesystem / linux 7.3 - Mailing list pgsql-performance

From Jeffrey D. Brower
Subject Re: ext3 filesystem / linux 7.3
Date
Msg-id 0a6f01c2f93a$6907bf50$0b02a8c0@pointhere.net
Whole thread Raw
In response to Re: ext3 filesystem / linux 7.3  (eric soroos <eric-psql@soroos.net>)
Responses Re: ext3 filesystem / linux 7.3  (Josh Berkus <josh@agliodbs.com>)
List pgsql-performance
>> This would indicate that the PG transactioning is complimentary to the
filesystem journaling, not duplication.

>It's both. See the -o data=journal|data=ordered|data=writeback mount
>time option.

I did a RTFM on that but I am now confused again.

I am wondering what the *best* setting is with ext3.  When I RTFM  the man
page for mount, the data=writeback option says plainly that it is fastest
but in a crash old data is quite possibly on the dataset.  The safest
*looks* to be data=journal since the journaling happens before writes are
committed to the file (and presumably the journal is used to update the file
on the disk to apply the journal entry to the disk file?) and the default is
data=ordered which says write to the disk AND THEN to the journal (which
seems bizarre to me).

How all of that works WITH and/or AGAINST PostgreSQL and what metadata
REALLY means is my bottom line quandary.  Obviously that is where finding
the warm and fuzzy place between speed and safety is found.

     Jeff


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