Configuring Data Block Size
The data block size is the amount of data written to each drive when striping data across drives. (The block size is also known as the stripe unit size.) The block size can be changed only when there are no volumes defined. The block size can be configured as 16 Kbytes, 32 Kbytes, or 64 Kbytes. The default block size is 64 Kbytes.
A cache segment is the amount of data being read into cache. A cache segment is 1/8 of a data block. Therefore, cache segments can be 2 Kbytes, 4 Kbytes, or
8 Kbytes. Because the default block size is 64 Kbytes, the default cache segment size is 8 Kbytes.
Note – The array data block size is independent of I/O block size. Alignment of the two is not required.
Selecting a Data Block Size
If the I/O initiated from the host is 4 Kbytes, a data block size of 64 Kbytes would force 8 Kbytes of internal disk I/O, wasting 4 Kbytes of the cache segment. Therefore, it would be best to configure
Applications benefit from the following data block or stripe unit sizes:
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■Online Transaction Processing (OLTP)
■Internet service provider (ISP)
■Enterprise Resource Planning (ERP)
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■NFS™ file system, version 2
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■Decision Support Systems (DSS)
■Data Warehouse (DW)
■High Performance Computing (HPC)
Chapter 2 Configuring Global Parameters 15