David Hendrix writes:

>I am a little concerned about Andy's comments regarding using raw partitions
>for DB and Logs.  When we had IBM on-site in Jan of this year, we
>specifically asked which "path" was best.  Therefore we implemented our
>servers using raw partitions.
>
>What potential problems are we talking about here?
>
>We are about to install a rather large server to service quite a few of our
>applications, and I would like to build this using a reliable configuration.

Hi David,

The kinds of problems I'm talking about are usually user-inflicted. For
example, if you try to start 'dsmserv' more than once (pointing to the same
database and recovery log), we've seen databases in raw logical partitions
become corrupted. If the files are under a JFS filesystem, this wouldn't happen
because the second iteration of dsmserv wouldn't even be allowed to open the
database. So you get the protection inherent in the filesystem. Note: I think
we will be putting some code in the ADSM server to prevent this particular
situation from happening when using raw logical volumes - in fact, it may
be in the Level 0.7 version of the server. But I wanted to point it out as
a potential trouble spot.
   We've also seen problems with users extending the size of the raw logical
volumes in order to increase recovery log or database space. I am fuzzy on the
details, as I've only heard this in my discussions with other level 2 support
folks.
   I'm not sure what the advantages of raw partitions are over JFS. If you're
thinking performance, that may not be the case -- I've spoken with developers
who say that they've even heard some cases where JFS performed better than
raw partitions. I've also spoken to people in ADSM performance who say that
rap partitions can perform better than JFS. But even those folks do not
recommend raw partitions.
   Because of the criticality of the database, I would recommend using JFS
files over raw partitions, unless there is a compelling reason to do otherwise.

Andy Raibeck
ADSM Level 2 Support
408-256-0130