Sun Microsystems Sun StorEdge T3 - Manual (Page 27)

Chapter 2 Configuring Global Parameters 15
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 32-Kbyte block sizes, causing 4-Kbyte
physical I/O from the disk. If sequential activity occurs, full block writes (32 Kbytes)
will take place. For 8-Kbyte I/O or greater from the host, use 64-Kbyte blocks.
Applications benefit from the following data block or stripe unit sizes:
■ 16-Kbyte data block size
■ Online Transaction Processing (OLTP)
■ Internet service provider (ISP)
■ Enterprise Resource Planning (ERP)
■ 32-Kbyte data block size
■
NFS™ file system, version 2
■
Attribute-intensive NFS file system, version 3
■ 64-Kbyte data block size
■ Data-intensive NFS file system, version 3
■ Decision Support Systems (DSS)
■
Data Warehouse (DW)
■
High Performance Computing (HPC)