Backup Exec 20.2 Administrator's Guide

Hardware

Some hardware-related variables which can affect performance include:

Confirm that the controller is rated for the tape backup hardware. If it is not, you may experience unexpected performance limitations.

System

The capacity and speed of the media server performing the backup, or the remote system being backed up, significantly affect performance. System activity during the backup also affects performance. Fragmented disks take a longer time to back up. Heavily fragmented hard disks not only affect the rate at which data is written to tape, but also affect overall system performance. Fragmented files take longer to back up because each segment of data is located at a different location on the disk. This fragmentation increases the time that is required to access the data. Make sure to defragment disks on a regular basis.

Memory

The amount of available memory affects backup speed. Insufficient memory, improper page file settings, or a lack of available free disk space can all cause excessive paging and slow performance. Make sure that every program and every process release the memory that it allocates when it starts. If a program or process does not release as much memory as it originally allocated, a memory leak occurs.

File types

An average file compresses at a 2:1 ratio when it is compressed using hardware compression. Higher and lower compression ratios occur depending on the type of files being backed up. If no compression is used, the tape device performs at its rated speed. Average compression ratios can double the backup speed. Image and picture files are fully compressed on disk. Hardware compression is performed by the tape device and not the backup software.

Compression

Successful compression can increase the tape drive's data transfer rate up to twice the native rate. Compression can be highly variable depending on the input data. Image files from a graphical program might compress at 4.5:1 or more, while binary files might compress at only 1.5:1. Data that has already been compressed or encrypted may expand by about five percent if you attempt to compress it further. This data expansion can reduce drive throughput.

Files

The total number of files on a disk and the relative size of each file affects backup performance. Disks containing fewer files, but where each file is large, run backups quickly. Backups run slower if a disk contains many small files. A large number of files which reside in the same directory path can be backed up more efficiently than files in multiple directory locations.

Block size

Larger block sizes can improve the compression ratio, which helps the drive achieve better throughput and more tape capacity. Make sure that the block sizes and buffer sizes are set properly. Throughput increases in proportion to the compression achieved, until you reach the drive's maximum throughput. Do not increase the block size beyond the default settings.

Network

The physical connection to a remote disk limits that disk's backup speed. The rate at which a remote server's hard disks can be backed up depends on the following factors:

A common cause of slow network backups is networking configuration. Features such as "full-duplex" and "auto-detect" may not be fully supported in every environment. To improve throughput, manually set the speed to 100 MB and the duplex to half/full for the server side. Find out which Ethernet port the server is connected to on the switch, and set the SWITCH PORT setting to 100 MB and half/full duplex. Do this for the backup server switch port, and any switch ports for computers being backed up.

If a full duplex backup is slower than a half duplex backup, full duplex may not be supported for your combination of NIC, driver, and switch. Contact the NIC and switch manufacturer for updated drivers, firmware, or other support documentation.

The NIC driver can be a common cause of slow throughput. The NIC driver can be easily overwritten by an operating system service pack. If a service pack has been applied and the driver has been overwritten, reinstall the Original Equipment Manufacturer driver.

Debugging

Debugging that is enabled for troubleshooting purposes can also affect system performance. Debugging that occurs through the Services applet is temporary. Cycle the services or restart the computer to stop the debugging. Debugging configured through the Windows Registry allows for continuous debugging. Leaving the services in debugging mode causes the logs to accumulate. To improve performance, either take the services out of debugging mode when the problem is resolved, delete the older debug files, or compress the logs directory.

Backup Exec Database

Installing the Backup Exec Database (BEDB) to an existing SQL instance that other applications use can also degrade performance. This is particularly relevant in a Central Administration Server (CAS) environment. Other applications may cause resource issues and use all the available resources within the instance.