Solaris Volume Manager Administration Guide

Sequential Access I/O

You can optimize the performance of your configuration in a sequential I/O environment, such as DBMS servers that are dominated by full table scans and NFS servers in very data-intensive environments. To take advantage of a sequential I/O environment, set the interlace value low relative to the size of the typical I/O request.

For example, assume a typical I/O request size of 256 Kbytes and striping across 4 spindles. A good choice for the stripe unit size in this example would be:

256 Kbytes / 4 = 64 Kbytes, or smaller

This strategy ensures that the typical I/O request is spread across multiple disk spindles, thus increasing the sequential bandwidth.

Note –

Seek time and rotation time are practically zero in the sequential I/O environment. When you optimize sequential I/O, the internal transfer rate of a disk is most important.

In sequential applications, the typical I/O size is usually large, meaning more than 128 Kbytes or even more than 1 Mbyte. Assume an application with a typical I/O request size of 256 Kbytes and assume striping across 4 disk spindles, thus:

256 Kbytes / 4 = 64 Kbytes

So, a good choice for the interlace size would be 32–64 Kbytes.