yesterday I was once again asked by a fellow ‘senior’ DBA I know, about the 300 second guideline for the PLE (Page Life Expectancy) counter. It never really ceases to amaze me how many people in our community are still not aware on how to interpret this value and be able to calculate a proper value for their specific situation. So to help everyone with the basics, the following link points to the blog posting by Paul Randal of SQLSkills.
In this posting he explains what this counter is really about and how it should be interpreted. This includes the info on how it relates to NUMA nodes. This is pretty essential info, so don’t skip this part and make sure you understand it.
Oowww and don’t forget, NUMA is something that will bite you in the ass (performance-wise) if you don’t know how it plays a part in your environment. Especially if you are running SQL in a virtual setup, talk to your virtualization admins and know how your servers (hosts) and VM (guests) are configured. But I will get some more info about that and what to look for, in a future posting.