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NetVault 12.4 - Administration Guide for Managed Service Providers

Introduction Getting started Configuring clients Managing catalog search Configuring storage devices
About storage devices SAN considerations Quest DR Series systems Quest QoreStor NetVault SmartDisk EMC Data Domain Systems Snapshot Array Manager Virtual Tape Libraries Virtual standalone drives Shared Virtual Tape Libraries Physical tape devices Storage tiers
Backing up data Managing policies Restoring data Managing NetVault Backup dashboard Managing jobs Monitoring logs Managing storage devices
Role-based access to manage storage devices Monitoring device activity Managing disk-based storage devices in list view Managing disk-based storage devices in tree view Managing the Snapshot Array Manager Managing tape libraries in list view Managing tape libraries in tree view Managing tape drives in list view Managing tape drives in tree view Adding shared devices
Managing storage media Managing user and group accounts Managing Tenant 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 the reporting utility Configuring NetVault Backup WebUI default settings Configuring NetVault Backup to use a specific VSS provider Configuring default settings using Txtconfig
Diagnostic tracing Managing diagnostic data Using the deviceconfig utility NetVault Backup processes Environment variables Network ports used by NetVault Backup Troubleshooting
Common errors Safe Mode in NetVault Backup

Configuring performance options for a tape drive

To configure performance options for a tape drive:
1
In the Navigation pane, click Manage Devices.
2
In the list of devices, click the icon to open the library that contains the drive, and then click the drive or the corresponding Manage Drive icon .
3
On the Tape Drive Management page, click Performance.
4
In the Drive Performance Options, configure the following settings.
 
Table 96. Drive performance options
Option
Description

Drive Block Size

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

NOTE: The drive block size should be the same size as the media block size for the VTL.

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

NOTE: The changes to the media block size settings are only applied to blank media items. If you are reusing a media item, make it blank first for these changes to take effect.

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:

1
Start the Registry Editor.
2
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).
3
Create the Parameters key, if it is not present.
4
Under Parameters, create the Device key, if it is not present.
5
Under the Device key, add the DWORD registry value MaximumSGList, if it is not present.
6
Calculate the hexadecimal value of MaximumSGList:
On 32-bit systems:
MaximumSGList = (Maximum Block Size / 4KiB) + 1
For example, if the block size is set to 256KiB, the value for this key is:
(256KiB/4KiB) + 1 = 65
The decimal value is 65 and the hexadecimal value is 0x41.
You can set the block size to any value from 64KiB through 1012KiB. The maximum value 255 is internally converted to 257 to make a block size of 1 MiB (1024 KiB).
On 64-bit systems:
On 64-bit systems, the default OS page size is 8KiB. The formula for calculating MaximumSGList is:
MaximumSGList = (Maximum Block Size / 8KiB) +1
Thus, the maximum value of 255 corresponds to a maximum media block size of 2MiB.
7
Reboot the system to apply the changes.

Drive Transfer Buffer Size

The transfer buffer or the shared memory is allocated in blocks of 32KiB. The default value is 8193KiB.Changing the default Drive Transfer Buffer Size option.

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:

•
Maximum size of a shared memory segment (SHMMAX)
•
Minimum size of shared memory segment (SHMMIN)
•
Maximum number of shared memory identifiers in the system (SHMMNI)
•
Maximum number of shared memory segments a user process can attach (SHMSEG)
•
Maximum number of semaphore identifiers in the system (SEMMNI)

 
•
Maximum number of semaphores in a set (SEMMSL)
•
Maximum number of semaphores in the system (SEMMNS)
•
Maximum number of operations per semop call (SEMOPM)
•
Semaphore maximum value (SEMVMX)

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.

5
To enable software compression for virtual tape drives, configure the following options.
 
Table 97. Software compression options for virtual tape drives
Option
Description

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 the compressed data size is less than 80 percent of the original data size, the data is backed up in its compressed form.
•
If the compressed data size is more than 80 percent of the original data size, the data is backed up in its uncompressed form.

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.

Compression Data Blocks

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

6
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.

 
Table 98. Optimal transfer buffer size of different drive types
Drive type
Optimal transfer buffer size (in KiB)

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

To check the status of an offline tape drive:
1
In the Navigation pane, click Manage Devices.
2
In the list of devices, click the icon to open the library that contains the drive, and then click the drive or the corresponding Manage Drive icon .
3
On the Tape Drive Management page, click Check, and then in the confirmation dialog box, click Check again.
If the device is operational, its status is changed to “Available.”

Changing the status of a tape drive

To change the drive status to online or offline:
1
In the Navigation pane, click Manage Devices.
2
In the list of devices, click the icon to open the library that contains the drive, and then click the drive or the corresponding Manage Drive icon .
3
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.
This operation does not physically take the device offline; it just makes the device unavailable for use in NetVault Backup.
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