[ic] SessionType & Performance

[Mike Heins]

Quoting Randy Moore (ramoore@axion-it.net):
> Hi all,
> 
> Can anyone offer info about the performance tradeoff's of the different 
> SessionType options?
> 
> The docs for the SessionType configuration directive suggest that the 
> 'File' type offers the best performance (and this is the default), but the 
> rest of the documentation seems to assume we should use GDBM or DB_File.
> 
> Which really offers the best performance on a reasonably powerful server?

File. The reason is that contending for lock on a DBM file can be a hotspot
for a busy server. And write speed for Storable on a local filesystem or
NFS is greater than 1MB per second on a fast system/network. 

> 
> Also, the docs say "Don't use this!" about the DBI session type.  What is 
> the danger there?

I am less worried about this than I was before it had much real-world
testing.  Basically, "don't use this" on a mirrored Oracle server with
very slow write speed, or a PostGres 6.5.x system, or anything with slow
write. We have installations that have very good luck with using MySQL.
(There is a system that uses MySQL that takes many thousands of
orders per month.)

It is not difficult to try them all and see which performs best for you.
It isn't much more than just setting up a session database DSN and
trying out the different SessionType settings.

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