Summary
This article describes how to tune the Netware operating system for use with DPX
Resolution
Purpose
DPX provides a number of parameters for tuning a Netware node for optimal performance. These recommended parameters cover a wide range of server environments, but may not be optimal for your system. In relatively few cases, further tuning is required. See "Understanding and Troubleshooting Netware Communication Problems" for further details if the suggestions here do not solve your performance or communication problem. Please refer to the support documentation on Novell's website at www.novell.com/ .
Performance
First, make sure that your switch/hub is configured properly. If the network is configured improperly with half-duplex devices interacting with full duplex devices, excessive collisions will occur which can cause connection problems. Performance is also hampered when the NIC or router is set to "auto-negotiating" for the card speed or duplex mode. Try setting these manually to the correct value. If the disks are compressed, it will slow performance. It takes a lot of CPU overhead to uncompress the data if the data is expanded. If Anti-Virus is enabled for file reads and writes, it will also hamper throughput. It is best to disable Anti-Virus software during backups and restores. There are also several system parameters that you can adjust to increase the speed. You can make the following changes using the "Monitor" utility. The changes to the "communications" parameters should make the most difference. Note that these suggestions are for high-traffic, high-powered servers. If the server has limited resources, increasing some of these settings may cause the server to abend. In addition, servers with more than 1000 users may require larger values for the Packet Receive Buffers and Directory Cache Buffers.
Monitor -> Server Parameters -> Communications
Minimum Packet Receive Buffers=500 (or 3 per connection)
Maximum Packet Receive Buffers=4000
Maximum Physical Receive Packet Size=4224
Monitor -> Server Parameters -> Directory Caching
Maximum Concurrent Directory Cache Writes=100
Maximum Directory Cache Buffers=4000
Minimum Directory Cache Buffers=500 (or 3 per connection)
Directory Cache Allocation Wait Time=0.5 sec
Monitor -> Server Parameters -> File Caching
Maximum Concurrent Disk Cache Writes=500
Dirty Disk Cache Delay Time=0.5
Monitor -> Server Parameters -> Miscellaneous
Minimum Service Processes=500 (or 3 per connection)
Maximum Service Processes=1000
New Service Wait Time=0.3 sec
Monitor -> Server Parameters -> Memory
Reserved Buffers Below 16MB=200 (Only for older HBA's that cannot address memory above 16 MB)
References: Novell TID 10023910, 10012765,
Communications Errors
To troubleshoot NetWare communication errors, you can specify TCP/IP parameters manually. Set the "Physical Packet Receive Buffers" size should be set manually. Receive buffers are used to store incoming packets from each of the networks attached to a NetWare server. The Maximum Physical Receive Packet Size (MPRPS) should be set according to the kind of network it is on. The cause of the most communication errors is a bad MPRPS. It is the first thing to adjust, if set incorrectly, before any of the other settings are changed.
Monitor -> Server Parameters -> Communications
Maximum Physical Receive Packet Size=4224
The following can be loaded at the console after TCPIP.NLM is loaded. These are not designed to increase performance, but to maintain shaky TCP IP connections.
SET USE SPECIFIED MTU = ON (default = OFF)
This setting forces IP to use a user specified MTU size. When this SET command is enabled, all the IP packets sent from the server go out with a specific packet size instead of a dynamic range between 576 and 5000.
SET MAXIMUM INTERFACE MTU = <MTU VALUE>
This value defines the MTU size that should be used when the SET USE SPECIFIED MTU parameter is enabled. If no value is defined, it will default to 576 Bytes. Set this to the same value as the Maximum Physical Receive Packet Size.
SET ALWAYS ALLOW IP FRAGMENTATION = ON (default = OFF)
This will allow IP fragmentation to take place when required. Some routers will try and fragment IP packets too through the segment and if this is enabled on the server it will not know how to interpret the fragmented packets and reject it causing the request to fail. You will see this with large IP packets normally.
SET TCP IP MAXIMUM SMALL ECBS = 2048 (default = 1024)
The most common use of these small ECBs are when doing IP Fragmentation. The default should be enough but if the application or system seems to slow down at different times, try allocating more small ECBs using this SET command.
SET TCP MINIMUM RETRANSMISSION TIMEOUT = 4 (default = 2)
If you detect a large number of retransmissions (check TCPCON -> STATISTICS -> TCP -> retransmissions), you may want to use this set command to change the retransmission timeout from the default of 2 TCP ticks (1 tick = 224 ms) to 4.
TCP CONNECTION ESTABLISHMENT TIMEOUT = 10 (default = 0)
This SET option can be used to change the TCP connection establishment timeout in ticks. Setting it allows users to drop the time the TCP connection stays in the half open state. Great care must be taken when using the SET command. It can have the advantage of quickly removing TCP connection errors, but it may have the disadvantage of deleting valid TCP connections that on a slower LAN if SET too low.
SET MAXIMUM PENDING TCP CONNECTION REQUESTS = 256 (default = 128)
When problems or delays exist trying to establish TCP connections to a Novell server, it may be due to the fact that the application has reached the maximum number of connections it can have in the half-open state. This SET command provides TCPIP with a way of increasing the size of the backlog queue from the default. This parameter will rarely need to be changed except for conditions of heavy traffic.