Network performance: Data Transfer Mode, Throttling, and Client traffic in Symantec Ghost

Article:TECH107981  |  Created: 2001-01-14  |  Updated: 2005-01-05  |  Article URL http://www.symantec.com/docs/TECH107981
Article Type
Technical Solution

Environment

Issue



This document describes what new features are available in Symantec Ghost 7.5 and later for controlling the speed and amount of network traffic that Ghost creates.


Solution



Symantec Ghost includes features that provide you with better control over Ghost's network traffic while running Ghost Console Tasks and GhostCast Sessions. These features are especially useful when it is necessary to perform cloning operations during normal business hours and network bandwidth is limited.

These new features include:
  • Data Transfer Modes: This option enables you to control the amount of traffic that is created when you run a Ghost Console Task or a GhostCast Session.
  • Throttle Options: These options enable you to reduce the rate at which Ghost sends data over the network when you run a Ghost Console Task or a GhostCast Session. Reducing the rate distributes Ghost's network traffic over a longer period of time, effectively reducing the load that Ghost puts on the network's performance.
  • Client polling interval: This option enables you to control the amount of traffic that is created by the Ghost Client at times when the Client is not participating in a Ghost Console Task or GhostCast Session.

The Data Transfer Modes and Throttle Options can be set in GhostCast Server, Ghost Console, or a DOS command line. To configure these options in GhostCast Server, click File and then Options. To configure these options in Ghost Console, click Tools, Options, and then Data Transfer.

The Client polling interval can be set in the Ghost Console. To configure these options click Tools > Options > Client > Interval. Setting the interval to zero (0) will stop the polling. Setting the interval to five (5) would delay a report from the client for 5 minutes.

Data Transfer Modes
Ghost includes a Data Transfer mode option for choosing which type of network packet will carry the Task data: multicast, directed broadcast, or unicast. The data transfer mode determines whether a packet will be passed through a hub, router, or switch, and on which subnets the packet will be distributed. This feature provides control over the amount of network traffic that is generated by a Ghost Console Task or a GhostCast session.

To set the Data Transfer mode, use the switch -U[U|D|M] at a DOS command prompt in the Advanced options on the Clone tab in a Task in the Ghost Console or in the "Command line" box in GhostCast Server. For instance, the following command line runs GhostCast Server in Directed Broadcast Mode to write the W2K.gho image to all computers on a single subnet in a GhostCast Session that is called Sales.

Ghostsrv.exe C:\images\w2k.gho sales -ud

The choice of an appropriate data transfer mode depends on the following points:
  • Whether the network supports multicasting
  • Whether the Task or session is a cloning operation, rather than another task such as a file transfer, Move the User, or Incremental Backup
  • How many computers are included in the Ghost Console Task or in the GhostCast session

Multicast mode
The Multicast mode is appropriate for sending a Task to many computers on a network. The Ghost Console and GhostCast Server automatically use Multicast mode unless you configure Ghost for a different mode.

When using Multicast mode, Ghost sends one set of data packets regardless of the number of computers that are in the Task or session. For instance, if a Task includes eight computers, then Ghost sends one set of data packets. The network's switches and routers handle the distribution and delivery of the packet to each client computer.

Note that if a network does not support multicasting, then forcing Ghost to use Multicast mode could cause Ghost to fail or could cause extremely heavy network traffic. Multicasting works over hubs and over IGMP-aware routers and switches.

Ghost does not support Multicast mode for file transfers, Move the User, and Incremental Backup.

Unicast mode
The Unicast mode is appropriate for sending a Ghost Console Task to a single computer or to small number of computers on a network that does not support multicasting.

When using Unicast mode, Ghost sends one set of data packets for each computer. For instance, if a Task includes eight computers, then Ghost sends eight sets of data packets. Increasing the number of computers in the Task greatly increases Ghost's affect on network performance.

Ghost uses Unicast mode by default when you run a Task that has a single computer as the target, or a Task that performs a Dump operation (Ghost creates an image file).

Directed Broadcast mode
The Directed Broadcast mode is appropriate for sending a Ghost Console Task to a large number of computers on a network that does not support multicasting, or to a large number of computers that are all in one subnet.

When using Directed Broadcast mode, Ghost sends one set of data packets to each subnet, regardless of the number of computers in each subnet. For instance, if a Task includes computers that are in two subnets, such as five computers in one subnet and three computers in another subnet, then Ghost sends two sets of data packets.

Ghost does not support Directed Broadcast mode for file transfers, Move the User, and Incremental Backup.

Throttle options
The GhostCast Server includes a Throttle option for slowing down the rate at which Ghost sends packets over the network. Slowing the rate effectively decreases network traffic, which improves network performance.

Data Throughput
Use the Data Throughput option to control the maximum amount of network bandwidth that Ghost will use.

Load Limit
Use the Load Limit option to control the speed at which the Ghost Console sends data to write an image to the client computers.

The maximum value that will work on your network depends on your network infrastructure, the number and type of network devices between the Ghost Console and the client computer, and the client hardware. To find the maximum value for a specific Task, run a Clone Task that is configured to write an image to the client computers. When you run the Task without a Load Limit, the speed that is displayed in the GhostCast Server is the network’s maximum value for a Load Limit.

To set the Load Limit from a DOS command line, use the switch -HL### where ### indicates the megabytes per minute. For instance, the following command line runs the Windows version of GhostCast Server in a GhostCast Session that is called Test. The session writes the image TestA.gho to a single computer at the maximum rate of 75 megabytes per minute.

Ghostsrv.exe C:\images\testa.gho test -HL=75

Dump Limit
Use the Dump Limit option to control the speed at which the Ghost Console receives data that "pulls" an image from a client computer and saves that image as a file.

The maximum value that will work on your network depends on your network infrastructure, the number and type of network devices between the Ghost Console and the client computer, and the client hardware. To find the maximum value for a specific Task, run a Clone Task that is configured to pull an image from a client computers. When you run the Task without a Dump Limit, the speed that is displayed in the GhostCast Server is the network’s maximum value for a Dump Limit.

To set the Dump Limit from a DOS command line, use the switch -HD### where ### indicates the megabytes per minute. For instance, the following command line runs the Windows version of GhostCast Server. The session creates a disk image and saves the image as the file diskdump.gho to disk 1 at C:\images at the maximum rate of 125 megabytes per minute.

Ghostsrv.exe C:\images\diskdump.gho disk1 -HD=125


Client polling intervals
After you install the Ghost Client on the client computers, the Ghost Client regularly polls the server for new tasks. When a slower network, such as a network that is configured for 10 megabits per second (Mbps) or slower, is already running under stress conditions, the polling messages can slightly reduce network performance.

Symantec Ghost includes a feature that allows you to turn these messages on or off or to adjust how frequently the Ghost Client sends the messages.





Legacy ID



2001121417073425


Article URL http://www.symantec.com/docs/TECH107981


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