NetVault 12.4 - Administration Guide

Perform software data compression

The default setting is OFF. To perform software compression, change the setting to ON. The data is compressed when it is transferred to the device during backup.

Compression decision switch

The value set for this option determines the minimum level of compression that must be achieved when data is compressed during a backup. For example, if you set the value to 80 percent, one of the following occurs:

If you specify 80 percent, a file size of a 100MB must be <= 80MB after compression however, the file size can be >80MB (like 81MB, 82MB, etc.), as the compression is done at block level.

When the specified compression level is not achieved for any block, in that case NetVault Backup backs up that block in its uncompressed form. Where, some blocks may be compressed and some blocks may remain in uncompressed form. Hence, in some case, the file size after compression can be greater than 80 percent.

The extent that data can be compressed depends on the data contents. Also the encrypted data cannot be compressed. With some files, compression may actually result in a file that is larger than the original uncompressed file.

Number of data blocks per compression unit

Type the number of data blocks per compression unit. The default block size is 8KiB.

Open disk media for Synchronous IO on Unix

The default setting is OFF. If your RAID system can respond instantaneously to synchronous IO writes, change the setting to ON. The ON setting allows multiple streams to generate output at similar rates resulting in similar jobs ending at the same time (but at the expense of overall throughput).

Under most circumstances, it is best to leave this option at the default OFF state to achieve best overall performance.

Amount of memory to assign for transfer buffers

The transfer buffer or the shared memory is allocated in blocks of 32KiB. The default value is 8193KiB.

Increasing the transfer buffer size can improve backup performance. To calculate the buffer size, use the following formula:

(<Total number of buffers> x 32KiB) + 1 byte

On Linux and UNIX systems, you require sufficient RAM and large Shared Memory segment. Before increasing the transfer buffer size, check the following settings on these platforms:

The total allowed shared memory is determined by the formula SHMMAX * SHMSEG. These values are often limited by the ulimit setting, and the command ulimit -a can be used to view these system settings.

On Windows, you require at least 2GB RAM and large virtual memory. You might also have to change the MaximumSGlist setting on the SCSI card.

For examples, see the Optimal transfer buffer size.

Number of media blocks to write at a time

We recommend that you do not change the default setting for this option.

If you change the value, record it because it is necessary to re-apply the setting if the drive is reinstalled. Restores require the same values that are set at the time of backup and fail if the settings do not match.

Number of media blocks to read at a time

We recommend that you do not change the default setting for this option.

If you change the value, record it because it is necessary to re-apply the setting if the drive is reinstalled. Restores require the same values that are set at the time of backup and fail if the settings do not match.

Lock transfer buffer in memory

Use this option to lock the allocated transfer buffer position in memory, and thus increase the potential performance and prevent other processes from using it when NetVault Backup is running.

The default setting is ON. Do not change the default setting unless otherwise advised by Quest Technical Support.

Gather statistics on device performance

The default setting is OFF. To log drive performance statistics, change the setting to ON. This information facilitates troubleshooting. However, it also increases the size of the NetVault Database.

Gather statistics on data channel performance

The default setting is OFF. To log Data Channel statistics, change the setting to ON. This information facilitates troubleshooting. However, it also increases the size of the NetVault Database.

Record drive performance

The default setting is ON. To record drive performance details with each job that uses the drive, use the default setting.

Length of time between sampling drive transfer rates

Specify the interval at which NetVault Backup records the drive transfer rates. The value is specified in number of seconds. The default value is 60 seconds.

Length of cleaning cycle

Specify the duration of the cleaning cycle. The value is specified in number of seconds. The default value is 350 seconds,

Issue a load command to start cleaning cycle

The default setting is ON. If the drive requires a load command to initiate a cleaning cycle, use the default setting.

List of ASC/ASQ codes that indicate cleaning has completed

Specify the ASC/ASCQ SCSI codes for cleaning, if necessary.

Use Generic Cleaning

The default setting is OFF. To use generic cleaning properties, change the setting to ON.