Hinweis
Für den Zugriff auf diese Seite ist eine Autorisierung erforderlich. Sie können versuchen, sich anzumelden oder das Verzeichnis zu wechseln.
Für den Zugriff auf diese Seite ist eine Autorisierung erforderlich. Sie können versuchen, das Verzeichnis zu wechseln.
This week I was involved in a conversation with Paul Randal relating to PLE per node vs PLE server wide.
There is an all-up PLE counter as well as individual, per NUMA node PLE counters. SQL Server Books Online describes the values as:
SQL Server Buffer Manager \ Page life expectancy – Indicates the number of seconds a page will stay in buffer pool without references.
SQL Server Buffer Node \ Page life expectancy – Indicates the minimum number of seconds a page will stay in buffer pool on this node without references.
The descriptions leave a bit to the imagination. It is pretty common place to ask someone about the all-up value and the assumption is a simple average of the individual node values. For example, using the following 4 Node values, the AVG = 1750 divided by 1000 = 175.
| 1000 |
| 2000 |
| 1500 |
| 2500 |
This is not the calculation used for all-up number. The Buffer Manager value is an average of the rates or the (Harmonic Mean.) Using the harmonic mean, run rates average, for this example the PLE = 155.
Paul outlines additional calculations and highlights the need to watch per node values for better management of your PLE targets in his post: https://www.sqlskills.com/blogs/paul/page-life-expectancy-isnt-what-you-think
Bob Dorr - Principal SQL Server Escalation Engineer