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Database Essentials
Administrative Planning : Data layout : Sizing your database areas : Block sizes
Block sizes
In the vast majority of cases, choose an 8KB-block size on UNIX, and a 4KB-block size in Windows. Selecting these block sizes conforms to the operating system block size, which usually yield the best performance. It is good practice to match or be a multiple of the operating system block size, if possible. Matching the database block size to the file system block size helps prevent unnecessary I/O, as shown in the following figure:
Figure 18. Matching database and file block sizes
In Windows, the operating system assumes that files and memory are handled in 4KB chunks. This means that all transfers from disk to memory are 4KB in size. The Windows operating system has been highly optimized for 4KB and often the performance at an 8KB setting is not as good as 4KB.
On UNIX operating systems, the block size is generally 8KB or a multiple of 8K. The block size is tunable. Generally, an 8K database block size is best on UNIX systems.
There are exceptions to every rule. The intention is to make a best estimate that will enhance performance and assist OpenEdge in meshing with your operating system.