Chapter 7: Performance Considerations

Hardware Considerations

The following hardware factors might affect SAS performance:

• the processor speed

• the amount of physical memory that is available

• the amount of disk space that is available for I/O

• the graphics adapter.

Not all of these factors will apply to your particular configuration or to the way in which you run SAS. Consult your system administrator for details.

Processor Speed

In general, a faster processor enables the computer to perform more operations per second. The more operations that can be performed, the more performance will improve.

The amount of processor cache that is available also influences performance. More processing cache will result in better performance.

The processor required to run SAS depends on the operating environment.

• In 32 “bit environments, you must have a PC that contains an Intel or Intel-compatible Pentium class processor.

• In 64 “bit environments, you must have an Intel Itanium Processor.

Memory

In general, more physical memory will result in better performance. Systems that have large amounts of available memory are capable of handling large amounts of data without swapping. Swapping uses the temporary space on the hard drive to store the data that could not be loaded into memory. However, memory is faster than the hard drive in manipulating temporary files and other system operations. Consequently, the more memory that is available, the less the hard drive will need to be accessed for these types of operations.

The minimum amount of memory required depends on the operating environment.

Table 7.1: Memory Requirements for 32 “Bit Environments

Operating Environment	Memory Requirements
Windows, Windows NT, Windows 2000 Professional, Windows XP Professional	128 MB minimum (More memory is recommended for improved performance.) 128 MB minimum of swap file space
Windows NT Server and Windows 2000 Server	256 MB minimum (More memory is recommended for improved performance.) 256 MB minimum of swap file space

Table 7.2: Memory Requirements for 64 “Bit Environments

Operating Environment	Memory Requirements
Windows Server 2003	1 GB minimum (More memory is recommended for improved performance.) 1 GB minimu of swap file space

Disk Space for I/O

An application uses I/O for data storage and data access. Therefore, faster I/O results in faster overall performance. The three factors that influence I/O performance are the disk controller and bus, the hard drive, and the hard drive configuration.

disk controller and bus

• In general, hard drive disk controllers that use their memory buffers to cache data have better throughput than conventional controllers. This can improve I/O performance.

  The type of I/O controller can affect I/O performance. SCSI and EIDE controllers generally offer higher bus speeds. A fast SCSI or EIDE bus used with the appropriate SCSI or EIDE drive can offer improved performance over other hard drives and controller types. Currently, SCSI controllers offer the best I/O performance.

hard drive

• Since SAS is heavily I/O oriented, access time and transfer rate are important to system performance. SCSI and EIDE drives generally have faster access times than MFM or IDE drives.

  Low disk space or a heavily fragmented disk can hinder I/O performance. It is recommended that you defragment your hard drive regularly to keep I/O performance from degrading.

hard drive configuration

• The hard drive configuration can have the greatest impact on I/O performance, especially on large server systems. Generally, a RAID configuration has better I/O performance than a non-RAID system. Consult your system administrator to determine the appropriate configuration for your computer.

Graphics Adapter

Since some SAS features use a significant amount of graphics memory, the type of graphics adapter that you use can make a difference in performance. Generally, if the same amount of graphics memory is available, AGP adapters are faster than PCI adapters. However, the type of adapter that you can use depends on your motherboard.

The amount of memory that is available on the adapter can impact the speed at which graphics are rendered. More memory usually results in better performance.