I just wanted to make everyone aware that Drupal on Ingres is maturing. I did some testing with it and worked with some folks at Ingres to move the yardsticks a bit. My experience with it is documented here:
http://community.ingres.com/forum/php/12353-drupal-ingres-10-0-a.html
http://community.ingres.com/forum/php/12361-drupal-client-ingres-db-serv...
http://community.ingres.com/forum/php/12599-maintaining-own-drupal-proje...
In a nutshell, the 10.1 Community Edition of Ingres and version 2.2.1 (not the latest!) of the PECL PHP driver works in a Drupal Client -> Ingres Server configuration (for the most part).
Ingres' own documentation on this can be found here: http://community.ingres.com/wiki/Drupal_on_Ingres_Documentation
I'll mention here that I had to increase the size of the Transaction Log. It is 256MB by default - I increased it to 1024MB. Ingres also has some pessimistic defaults (e.g. system_isolation=serializable) but I didn't spend anytime optimizing it.
Alas, priorities have shifted and I probably am going to have to put this on the backburner for a bit - it would be great if others took up the cause! Ingres has some nice enterprise features that MySQL (natively) doesn't, like online backup (yes, I know it's coming to MySQL), encryption-at-rest, etc.
(Acquia Google Alert bait) It would be nice if Acquia made some noise about it too since they espouse enterprise but still only support MySQL.
Cheers