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| File system creation guidelines | ||
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Follow these guidelines when creating VxFS file systems:
Specify the maximum log size when creating file systems for databases.
Except for specifying the maximum log size and support for large files as required, use the VxFS defaults when creating file systems for databases.
Never disable the intent logging feature of the file system.
For database logs, create a single file system using a simple (and mirrored, if necessary) volume. Put the other tablespaces and database files on separate file systems created on striped, striped and mirrored, or RAID-5 volumes.
When using the command line, use the mount points to name the underlying volumes. For example, if a file system named /db01 is to be created on a mirrored volume, name the volume db01 and the mirrors db01-01 and db01-02 to relate to the configuration objects. If you are using the vxassist command or the GUI, this is transparent.
Choose a file system block size that matches or is a multiple of the PAGESIZE parameter in the create database or create tablespace statement for your DB2 database or tablespace. The PAGESIZE parameter is defined in the create database or create tablespace statement.
It is possible to have a file system block size that is smaller than the database page size because the database page-size limit can be bigger than the file system block size. It is fine if the file system block size is smaller than the database page size because VxFS will not perform multiple I/O operations for each database I/O operation. VxFS is capable of performing I/Os with multiple blocks. For example, if your database page size is 8k and your file system block size is 4K, VxFS can put two 4k blocks together to perform one 8k database I/O operation. The DB2 instance will also need data in EXTENTSIZE, which is a multiple of PAGESIZE. These page size rules also apply for extent size.
When creating the file system, set the number of file system blocks in the intent log so that the log size is 16MB. For example, if the file system block size is 8K (that is, 8192), it will take 2000 blocks to make a 16MB log (2000 x 8192 = ~16MB). If the file system block size is 4K (that is, 4096), then twice as many blocks as in the 8K case would need to be allocated (4000 in this example).