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PERFORM.TXT
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1992-10-06
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TECHNICAL BULLETIN PERFORM
LANtastic Performance Issues
The following information is based on in-house testing of
LANtastic. If you are not a registered LANtastic owner, your
questions should be directed to our technical sales staff at
(602) 293-6363. Any questions or comments on this bulletin may
be forwarded by FAX (602) 293-8065 or mailed to: Artisoft Inc.,
691 East River Road, Tucson, AZ., 85704, ATTN: Technical Support.
GENERAL HINTS AND TIPS
INCREASING PERFORMANCE OF LANTASTIC NETWORKS
"What can I do to speed up my LAN?" A very common question, and
one to which there is unfortunately, no cut and dried answer.
Network performance depends on many things. Getting the best
performance out of your particular installation may require a
little experimentation. This bulletin presents a discussion of
some of the major factors that affect performance, and a few
general suggestions for improvement.
Choosing your Hardware
When you're choosing the hardware for your LAN, keep in mind that
the things that make a fast computer are also the basic
ingredients of a fast network. A fast processor, fast memory and
a fast disk drive all help to provide better network speed. For
best performance, you should choose fast, well balanced
components. The two biggest factors are CPU speed and hard disk
speed.
It's fairly easy to find fast computers and fast disk drives out
there in the marketplace, but for the best results make sure that
the components you buy are well matched. If you install a high
performance disk drive in a 4.77 Mhz XT, your network will be
slow because the computer's CPU won't be able to move data around
fast enough to keep up with the drive, let alone the rest of the
network. Similarly, if you install an old 20mb MFM drive in your
386-33, the fast processor will spend a lot of time waiting
around for the old drive, as will the rest of your network users.
The transmission speed of the adapter cards you choose will also
make a difference. With reasonably fast machines, upgrading from
a LANtastic 2mbps adapter to a new Artisoft Ethernet adapter can
approximately double the throughput of the network. Again,
balance is vital. If you have a slow processor, switching to
Ethernet may not make much difference -- the 2mbps adapter has a
coprocessor that handles all the low level NetBIOS processing,
whereas the Ethernet adapter relies on the computer to handle
everything.
Optimizing Software Performance
Now that we've dealt with hardware selection; let's see what can
be done to improve the performance of existing installations.
First, let's tie down what we mean by the "speed" of the LAN.
There are really two things at issue here, the physical
transmission speed of the hardware, and the effective throughput,
or how fast data gets from one place to another on the LAN.
Assuming for now that the hardware is fixed and immutable, here
are some suggestions for getting the best throughput with your
particular application.
Optimizing Network Configuration
There are two major configurations of the network that will
greatly benefit overall network performance.
The first is simply using LANtastic's ability to have more than
one server on the network. Splitting up network tasks so that
different programs are run on separate servers will decrease the
load on each individual server, this will improve the servers
response (and on a non dedicated server improve the performance
of the computer for the person sitting at the keyboard).
The next is setting up a dedicated server (while LANtastic is a
Peer to Peer network - Artisoft considers a dedicated server to
be only a special case of peer to peer networking). A dedicated
server can be specifically tuned to optimize the performance of
the Network portion of the computer at the detriment of the
Workstation (keyboard) portion of the computer.
This is done by using the RUN_BURST command line switch (on
AILANBIO with versions of LANtastic prior to 4.1, on both
AILANBIO and SERVER with version 4.1 and greater).
This switch controls the amount of time that the program (either
netbios or server) devotes to processing network tasks. The
higher the value the longer amount of time allocated. Since both
REDIR and SERVER release control if there are no tasks waiting
neither switch will conflict with the other. Setting these
switches to the max 254 will give optimum performance for a
dedicated server.
In a dedicated server, memory no longer is a major consideration.
Large sizes for the servers caching and buffers should be
experimented with. (See server buffering below.)
Another command that is useful for a dedicated server is the
ALONE command included with v4.0 and higher. When the server
program is used to access a resource on the server, it first
swaps out all the DOS stacks and control memory. It does this so
a foreground task can coexist with the server running in the
background. On a dedicated server Alone tells the server that
there will NEVER be a program running on this machine in the
foreground using DOS and so server saves time by NOT swapping
into and out of DOS. This means that you cannot run a TSR
(Terminate and Stay Resident program) on this dedicated server
that will use dos calls.
General Improvements
FASTOPEN
Running the DOS FASTOPEN command will improve network speed
considerably(except with MSDOS 5.0 because of a reported problem
in this version's FASTOPEN). FASTOPEN stores the location on the
hard disk of each previously opened file to make repeated access
to this file much faster.
SEEK CACHE
LANtastic 4.1 contains a new cache built into the server program,
SEEK CACHE. SEEK CACHE caches each users position within open
random access files. Typically a seek cache will significantly
affect performance of random access file operations if:
1> Files being accessed are relatively large.
2> The files are kept open and accessed frequently.
The optimum size for the SEEK CACHE is the SIZE of database
files/cluster size (typically 4096)* 32 + the Number of files
*32.
RESOURCE CACHE
When a user on LANtastic accesses a resource, LANtastic has to
check the resources Access Control List (ACL) to see what
permissions the user has. This requires loading the resource
information from the hard disk and checking it. To improve
performance with LANtastic NOS 4.1 resource caching can be
enabled on a server. This means that as each resource (disk or
printer) is accessed it's access information is stored in a
permanent cache in the server. There should be one cache
specified for each commonly used resource. If a server has
several resources, but only a few are normally accessed, the
cache number can be set to the number of commonly used resources
+1. The caches are flushed and used on a least frequently
accessed algorithm so system performance will be only slightly
affected.
INDIRECT FILE ACL's
Indirect files will greatly effect network performance, with
LANtastic NOS 3.0x eliminate the I from each disk resources
Access Control List. With NOS 4.xx the I ACL has already been
eliminated. With the I ACL in place each time a file is opened
the NOS checks to see if the file is an indirect file. If you
are not using indirect files eliminating this ACL will save time
when a file is opened.
SERVER AUDITING
Indirectly, server auditing can also have a great effect on
network performance. If auditing is enabled and the audit files
are not cleared on a regular basis this file can grow very large.
This by itself is not a problem; but since auditing requires that
an entry be made to this file every time an audited function is
used, the time spent seeking to the end of this file will
increase as the file size increases.
SEND SERVER ID
You can reduce the load on heavily used networks by disabling the
Send Server ID selection in NET_MGR, Server Startup Parameters.
With this selection enabled the server sends out a message once
every retry period (55ms x retry_period setting), this message is
just that the machine is a server and available. If your system
is using batch files this message is not needed. If the server
name is known, it can be logged into even if the server is NOT
sending out it's ID.
DISK CACHING
Adding a disk cache to the server also helps performance in
almost all situations. Disk caching programs work by storing
frequently requested information in memory. This reduces the
number of physical accesses to the disk. Since accessing memory
is almost always faster than accessing the disk drive, caching
can greatly improve the disk performance of your network.
The LANtastic disk caching program; LANcache, is specifically
designed to work with LANtastic networks. It caches disk writes
as well as disk reads and when it actually does have to write to
the disk, it does so as a background operation so that CPU
operations can continue.
Choosing the Best Buffer Settings
Beyond these general changes, getting the best performance out of
your specific application is a matter of fine tuning several
parameters. LANtastic has four sets of buffers, each of which can
affect performance in specific situations.
REDIR Buffers
It takes the network about the same amount of time to send 1 byte
of data as it does to send 256 bytes of data. Every packet sent
over the network takes time to construct and time to process.
Given this, it makes sense to include as much data as possible in
each packet -- it keeps the network overhead impact to a minimum
and reduces network traffic. The REDIR program accomplishes this
by buffering network requests at each machine. Here's an example
of REDIR's buffering in action:
You are creating a file of customer names on the server and
adding data to it. You type in the names one at a time and
your program writes the names to the data file one at a
time. Rather than issue a network send for each name, the
data gets stored in the local REDIR buffer until you close
the file or fill the buffer. At that point, REDIR issues a
single request to send the entire buffer.
REDIR buffers read requests similarly. If you request an amount
of data smaller than the REDIR buffer, REDIR requests one buffer
full of data from the server. Then, if you request the next
sequential piece of data, REDIR can supply it to your program
without even making a network request.
REDIR buffers are only used for small (small means smaller than
the REDIR buffer size) sequential reads or writes to files that
are NOT opened in the sharable mode. If you read or write blocks
of data larger than the REDIR buffer, the network software
bypasses it and moves data directly from the applications buffer
directly to the NetBIOS. The ideal REDIR buffer size then, would
be about the average size of the packets that your network
typically sends and receives. You can set the size of the REDIR
buffers with the SIZE= command line switch.
The number of REDIR buffers can also affect the performance of
many applications. If you allocate multiple REDIR buffers using
the BUFFERS= command line switch, the network tries to associate
each file opened in the non sharable mode. Network printers are
handled just like other files. Ideally, you should have a buffer
available for each open non sharable network file. If you have
more files than available buffers, the network flushes the least
recently used buffer and assigns into the new request.
WordPerfect is a good example of a program that is affected by
the number of buffers. If you have only one buffer allocated,
printing can be very slow because WP has to read the document and
send data to the printer with the same buffer. The buffer gets
continually filled and flushed, back and forth, with printer data
and document data. In this situation, allocating just one more
buffer allows WP to use one buffer for document reading and
another for printing.
Server Buffers and Tasks
A server buffer is at the other end of a REDIR buffer. When, for
example, a workstation makes a read request, the server reads one
server buffer full of data, beginning with the information
requested. If the workstation then asks for the next piece of the
same information, the server can get it from the buffer instead
of physically reading the hard disk.
The server buffer size can be changed from the Server Startup
Parameters option in the NET_MGR program. Be aware that bigger
isn't necessarily better -- as with REDIR buffers, the optimal
size is somewhere around the average size of the packets that
will be transferred across the network by your application. One
server buffer of whatever size you select is allocated for each
network task. Large network buffers will greatly effect the speed
when moving large amounts of sequential data across the network.
Loading programs, using a word processor, and using a cad program
are all examples of the type of applications and use that can
benefit from large server buffers.
When a workstation submits a request to a server, the server will
work on the request until the task is finished, or the timeslice
allocated to the server is over. If the server is set up with
only one network task, instead of switching, the server will run
the request to completion and other incoming tasks will be queued
up behind it. If server tasks are higher, the server can process
several tasks in one active period. One task can actually be
buffered in the server while another in being processed.
If you're a using network adapter with a coprocessor, like our
Enhanced 2mbps adapter, increasing the number of network tasks
(with the Server Startup Parameters option of NET_MGR) will give
you a big performance boost. While the coprocessor is busy
working on one task, the server's CPU can work on another. This
advantage is multiplied if you have more than one coprocessor
equipped adapter in a server. In fact, with three or four 2mbps
boards in a dedicated server and a corresponding number of
network tasks, you can achieve a continuous throughput comparable
to that of an Ethernet network with an equal number of stations.
As a plus, you've got built-in redundancy -- the workstations
connected to each adapter will function as separate networks. If
one segment fails because of cabling or adapter problems, the
rest will still operate.
SERVER REQUEST SIZE
With NOS 4.xx a new parameter has been added to change the size
of the server request buffer. The REQUEST_SIZE= is set to 14
bytes by default. If a request from a workstation is smaller than
this buffer, the server will be able to act directly on this
request. If the request is larger than the request buffer, it
must be buffered by the SERVERS initial send buffer, and system
overhead is increased. The value of 14 is chosen specifically
for LANtastic. This 14 byte buffer is large enough to tell the
server what type of operation and how many bytes the total
operation will take.
There are some natural breaks in the size of this buffer. The
default will handle only the very smallest network tasks, lock,
unlock, closing a file, etc. At 60-70 bytes most network
activity except reads and writes are processed without additional
buffering, and from 600-2048 small reads and writes are processed
without additional server buffering. This parameter should NOT
be set larger than the AILANBIO Initial Send Buffer. One request
buffer is allocated for each user in MAX USERS (LOGINS= command
line switch).
LOCK HOLD TIME
Artisoft has discovered that setting the lock hold time higher
than 0 with LANtastic v4.1 can have an adverse effect on the time
required to open a file. This parameter should be used
cautiously. If your use of the network entails opening and
closing a large number of files, then this parameter should be
set to a low value. If your use of the network involved
accessing a large common data file, then increasing the value of
this parameter will help performance.
NetBIOS and Adapter Card Memory
With LANtastic v4.xx ethernet cards, you can increase the netbios
packet size. This can have an effect on the system speed when
loading programs and performing large sequential reads and
writes. Increasing the PACKET_SIZE beyond 1500 bytes moves the
network out of IEEE802.3 standards and may cause problems if you
are using third party IEEE devices like routers or bridges.
With our AE-2 card, there's an easy way to get a performance
boost on heavily loaded networks. You can upgrade the adapter
from its default 16K configuration to a full 64K of RAM. It is
fairly easy to tell when this upgrade is needed. Start the
network; if after 10 minutes of use lancheck shows network
resource exhuasts, increasing the memory on the adapter will help
network performance.
Effects of Changing Buffer Sizes
Keep in mind that on systems with only two or three stations,
changing the buffer configuration may not have any measurable
impact on speed. In any case, increasing the size and number of
REDIR and SERVER buffers uses memory and can slow down programs
running on the server. If your application performance is
critical, consider setting up a dedicated server for your most
used application programs and printers.
Running Applications on the Server
To get the best performance out of your network when you run
applications on a server, you should always use the server as
though it was a remote workstation: log in and access the
application through network drives. Using the server locally,
without logging in, places you in contention with the rest of the
users and network performance can suffer. If you log in, the
server will schedule you along with the rest of the network users
and everyone will get good performance. This does NOT mean that
you should issue NET USE commands that use a drive over itself,
IE NET USE C: \\SERVER\C-DRIVE. This can cause problems. It is
better to create a common network redirection ie NET USE G:
\\SERVER\C-DRIVE and have ALL workstations (even the server)
access the program off of G:.
Increasing Print Speed
One of the slowest things about printing to a network printer is
spooling to the hard disk. With LANtastic NOS 3.0 and above you
can easily increase the print spooling speed by spooling to a RAM
disk. To change the spooler's location, use the Change Spool
Location option of NET_MGR's Queue Maintenance function. You
must be sure that the ramdisk is large enough to hold both the
largest file printed and all print requests that may be submitted
at one time. The spooler will exit with an error if there is not
enough space available on this drive.
PRINTER BUFFERS
As with REDIR and server buffers, increasing the size of your
printer buffers can improve printing speed. If your server has
more than one printer attached, increasing the number of printer
tasks will allow it to print to more than one printer
simultaneously. Artisoft has determined through testing that with
some applications running on the server optimum printing is
achieved with printer tasks set to 1 no matter how many printers
are attached to the server. Notably these applications are
Windows 3.x, Clipper 5.0, and Lotus products. If you notice slow
printing when running one of these programs on a print server,
you can increase print speed by setting printer tasks to 1 and
setting cps in the printer resource to 9600.
ARTISOFT, Inc. makes no warranties as to the completeness or
accuracy of this document. LANtastic is a registered trademark
of ARTISOFT, Inc. Brand names and product names are trademarks
or registered trademarks of their respective companies.