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NetVault 11.3 - Administration Guide

Introduction Getting started Configuring clients Configuring storage devices Backing up data Managing policies Restoring data Managing jobs Monitoring logs Managing storage devices
Monitoring device activity Managing disk-based storage devices in table view Managing disk-based storage devices in tree view Managing tape libraries in table view Managing tape libraries in tree view Managing tape drives in table view Managing tape drives in tree view Adding shared devices
Managing storage media Managing user accounts Monitoring events and configuring notifications Reporting in NetVault Backup Working with client clusters Configuring default settings for NetVault Backup
About configuring default settings Configuring encryption settings Configuring plug-in options Configuring default settings for post-scripts Configuring default settings for Verify Plug-in Configuring Deployment Manager Settings Configuring Job Manager settings Configuring Logging Daemon settings Configuring Media Manager settings Configuring Network Manager settings Configuring Process Manager settings Configuring RAS device settings Configuring Schedule Manager settings Configuring Web Service settings Configuring Auditor Daemon settings Configuring firewall settings Configuring general settings Configuring security settings Synchronizing NetVault Time Configuring default settings for global notification methods Configuring the reporting utility Configuring NetVault Backup to use a specific VSS provider Configuring default settings using NetVault Configurator Configuring default settings using Txtconfig
Diagnostic tracing Using the deviceconfig utility NetVault Backup processes Environment variables Network ports used by NetVault Backup Troubleshooting

Configuring performance options for a tape drive

On the Tape Drive Management page, click Performance.
In the Drive Performance Options, configure the following settings.

Drive Block Size

This option specifies the block size used for read and write operations. The default value is 64KiB.

You can change the media block size in increments of 1KiB, but many devices may only accept a value in the multiples of 4KiB or 32KiB.

Increasing the block size can reduce the number of times a backup needs to read data and write it to media. However, large media block sizes do not always imply an overall faster backup. The maximum block size is limited by several factors, such as the OS, SCSI adapter, drive make, drive model, and drive type.

On Linux and UNIX systems, you can increase the media block size for optimum performance.


On Windows, you might be required to change the registry setting MaximumSGList to use block sizes larger than 64KB. Before changing this setting, check that the SCSI bus is only used by the tape devices. If other devices also use the SCSI bus, this registry change might prevent them from working. If you want to apply these changes only to a specific channel on the HBA, consult the hardware vendor.

To change the registry setting on Windows, follow these steps:

Open the key [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\ Services\<HBA Vendor>\Parameters (where <HBA Name> is specific to your SCSI card — for example, QL2200 for a Qlogic 2200 card).
Create the Parameters key, if it is not present.
Under Parameters, create the Device key, if it is not present.
Under the Device key, add the DWORD registry value MaximumSGList, if it is not present.

Drive Transfer Buffer Size

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.

Software Data Compression

To perform software compression, select this check box. The data is compressed when it is transferred to the device during backup.

Compression Threshold

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. If the specified level is not achieved, NetVault Backup backs up the file in its uncompressed form. The extent that data can be compressed depends on the data contents. Encrypted data cannot be compressed. With some files, compression may actually result in a file that is larger than the original uncompressed file.

Compression Data Blocks

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

Click OK to save the settings and close the dialog box.

Optimal transfer buffer size

The following table provides examples of the optimal values that can be used for some drive types.

Fast Modern Tape Drives

For example, LTO series, SDLT, and SAIT

65537 (64MiB + 1KiB)

Medium Speed Tape Drives

For example, DLT8000, DLT7000, and AIT-3

32769 (32MiB + 1KiB)

Older Professional Tape Drives

For example, DLT2000, DLT4000, and AIT-2

16385 (16MiB + 1KiB)

Older Low Capacity Low-end Drives

For example, EXB-8505, AIT-1, and DAT

8193 (8MiB + 1KiB)

Checking the status of a tape drive

On the Tape Drive Management page, click Check, and then in the confirmation dialog box, click Check again.

Changing the status of a tape drive

On the Tape Drive Management page, click Online or Offline:
If the device is offline, click Online to bring it back online.
If the device is online, click Offline to mark it offline.
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