Clariion Cache : Page Size

There are 4 different Cache page size settings available in a Clariion; the default size is 8kb with other available options at 2kb, 4kb and 16kb.

Based on your applications you should customize your Cache page size. Applications like Exchange data blocks consume 4kb page size, SQL uses 8kb and Oracle uses 16kb.

Let’s say you are running Exchange and SQL on your Clariion. Your defined cache page size is 4kb in the Clariion. Each Exchange data block will occupy 4kb cache page size and the application along with cache will work excellent. Now assume SQL is running on the same machine which has a data block size of 8kb, so every SQL block will be broken down into 2 separate pages in cache at 4kb each. Now imagine running Oracle on it which has a data block size of 16kb, here each data block will be broken into 4 cache pages, at this point your applications will start having backend performance issues.

In this scenario Exchange will work perfect, SQL with a little performance impact and Oracle heavy impacted with 4 cache pages per data block.

Now let’s imagine a scenario where you are using 16kb page size for Oracle as the primary application for that machine. Time goes by and the machine is upgraded with disk etc and used for SQL and Exchange along with Oracle. Your page size is 16kb, Oracle applications run fine. SQL starts putting its block of data in cache at 8kb, but your size is 16kb, wasting 8kb per block of SQL data that comes in. Similarly with Exchange you have 4kb block size, and you are wasting 12kb per block of data in the cache. In these scenarios you will fill up your cache much faster not with data, but with wasted open space rather called holes.

Best recommendation would be to have separate machines (Clariion) based on the applications you run on them. If you are running SQL and Exchange primarily, it might be a good idea to run it at 8kb Cache size on one Clariion. For Oracle possibly run another machine at 16kb Cache size. If you try to slam all of them together, either the applications will have issues or the cache will have issues or worst you will see performance issues throughout your Clariion.