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FW: Info on Network Load Balancing for Magic
-----Original Message-----
From: Ken Stainsby
To: Finnerty, John
Cc: Helly, Dan
Sent: 5/9/03 7:24 AM
Subject: Info on Network Load Balancing for Magic
Network Load Balancing Alternatives for Magic
Load balancing is the process of dividing the amount of work that a
computer performs between two or more computers so that more work gets
done in less time and all users get served faster. In general, load
balancing can be implemented with hardware, software, or a combination
of both.
There are 3 (three) primary methods of load balancing. Only the third
type, Microsoft Network Load Balancing, has been tested with Magic and
is therefore recommended for use with Magic.
1. Round Robin DNS is a simple and low-cost scalability and performance
solution for enabling a limited form of load balancing for Internet
server farms.
• Advantage: usually comes free of charge as a standard feature of most
popular operating systems, such as Microsoft Windows NT 4.0 with Service
Pack 4 and Windows 2000
• Disadvantage: is not a high-availability solution.
2. Load-balancing switches such as Cisco, F5, and Alteon products,
redirect TCP/IP requests to multiple servers in a server farm.
• Advantage: highly scalable, interoperable solution that is also very
reliable. Much better and more scalable than using Round Robin DNS.
• Disadvantages:
1-can be quite expensive
2-requires multiple switches to avoid making the switch the single point
of failure for the entire Web application.
3. Microsoft Windows 2000 Network Load Balancing (NLB)
Advantages: (there are no significant Disadvantages)
is less expensive than a load-balancing switch
avoids having a single point of failure.
is available in:
Windows 2000 Advanced Server
Windows 2000 Datacenter Server
Windows 2000 Server [rather than Advanced Server] as part of Microsoft
Application Center 2k
provides high availability and high scalability
utilizes a common virtual IP address
transparently partitions client requests across multiple servers
Adding Web servers can provide near-linear scalability (meaning that
throughput increases linearly with additional servers) when guidelines
for good design are followed. For more information see the Microsoft
article Building a Highly Available and Scalable Web Farm, available at
the Microsoft website:
<http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnduwo
n/html/d5nlb.asp>
The near-linear scalability in NLB means that although one machine is
capable of handling 300 concurrent users, adding a second machine does
not double this number. With additional machines the sum of all
concurrent users is reduced by a 25% overhead cost across all machines.
Therefore, the total number of concurrent users for two machines is 450
(instead of 600). Although an NLB cluster can include up to 32 machines,
Microsoft recommends no more than eight (8). If further capacity is
required, configure additional NLB clusters on more subnets. Using NLB
clustering necessitates a larger database server than a single-server
environment.
In addition to the common external IP address for the cluster, each
server in the cluster responds to a dedicated network address as well.
So, each machine responds to two network addresses:
• a cluster network address, and
• a dedicated network address.
Network Load Balancing is implemented using a network driver that is
logically placed between the higher-level protocol TCP/IP and the
network adapter of the host. All the cluster hosts receive the incoming
traffic. The NLB network driver acts as a filter and allows the host to
process only a part of the incoming traffic. The incoming requests are
accepted according to the NLB settings for the host.
The benefits of deploying NLB include:
• Fault tolerance. Network Load Balancing automatically detects a
nonfunctional host and can recover from it. In the case of an offline
host, the incoming traffic is distributed across all the servers. It
requires no additional hardware to avoid single points of failure.
• Higher scalability. Network Load Balancing supports clusters of up to
32 computers, although smaller clusters of 16-24 computers usually
result in better resource utilization.
• Higher performance. Unlike most load balancing switches, the
performance of MS Network Load Balancing automatically improves with the
speed of the cluster hosts and local area network (LAN), ensuring that
the load balancing will never become a bottleneck as LAN and host speeds
increase.
• Manageability. You can specify load balancing for a single TCP port to
customize processing load for a host. You can also block access to
certain ports.
• Ease of use. MS Network Load Balancing installs a standard networking
driver component and does not need any special hardware to run.
- NLB distributes incoming TCP traffic using a statistical algorithm
based on server-load percentage settings.
- NLB provides dynamic scaling by automatically accommodating the
addition and removal of cluster members without affecting clients.
For more information see the article Load Balancing COM+ Components,
available on the Microsoft website:
http://www.microsoft.com/technet/treeview/default.asp?url=/technet/prodt
echnol/acs/evaluate/LB-Cmpnt.asp
<http://www.microsoft.com/technet/treeview/default.asp?url=/technet/prod
technol/acs/evaluate/LB-Cmpnt.asp>
Windows Load Balancing Service (WLBS) on Windows NT 4 Server Enterprise
Edition has not been tested with Magic, and therefore is not supported.
Ken Stainsby
Nashco Consulting Ltd.
Office: (866) 590-0846
Cell: (403) 804-7828
Fax: (403) 206-7693
Email: ken@nashco.ca <mailto:ken@nashco.ca>
Web: www.nashco.ca
<file:///C:Documents%20and%20SettingsKenApplication%20DataMicrosoft
Signatureswww.nashco.ca>
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