Ref: 99960015
Title: 3+Open For 3Servers Release Note Number 6328-00
Date: 02-01-89

Copyright 3Com Corporation, 1991.  All rights reserved.


.BR;3+Open for 3Servers Release Notes
.BR;Part Number 6328-00
.BR;February 1989

3+Open system software for 3Servers contains an OS/2* and LAN Manager
program that has some important differences from previous versions of
MS OS/2.  This product contains sophisticated disk caching software
that optimizes the performance of OS/2 in a multiuser environment.
This new software also provides support for disk partitions greater
than 32 megabytes.

Before You Begin
This document is a supplement to the 3+Open for 3Servers Installation
and Setup Guide and Microsoft Operating System/2 Setup Guide, that are
provided with the 3+Open software package.  When you are ready to
install the 3+Open system software, refer to the two guides in
addition to this supplement for hardware and software requirements.

In This Guide

This supplement discusses:

Changes to the file allocation table (FAT) system

Utilities that were changed for this product

Technical improvements and changes for this product

The new cache program

.BR;Installation
.BR;Before you install 3+Open system software onto your server, you need
to decide:

.BR;How you will partition the server's hard disk.
.BR;How large a disk cache you will need.

The next sections provide this information.

.BR;What is Disk Partitioning?
.BR;A hard disk can be organized into separate sections called partitions.
Partitions divide your hard disk into different areas and allow you to
better organize your files.

Individual partitions are assigned drive letters to identify them.
For example, in addition to drives A (floppy-disk drive) and C (hard
disk drive), you may also have drives D, E, and F on your hard disk
after partitioning.

With this product you can repartition if you want a single disk
partition, to store more than 32 megabytes of information.  For
example, you can store a database larger than 32 megabytes on your
server's hard disk.

Refer to Appendix A in the 3+Open for 3Servers Installation and Setup
Guide and Chapter 4 of Microsoft Operating System/2 Setup Guide for
additional information about disk partitioning.

.BR;What is Disk Caching?
.BR;Disk caching improves performance by using high-speed random access
memory (RAM) as a temporary storage location for data that is being
read from or written to the hard disk.  Read caching works by reading
large blocks of data from the disk and storing it in the cache.  This
way when the same data is requested again it is instantly available.

Write caching stores data in the cache temporarily, where it is
available for immediate update if needed.  Write caching also provides
temporary storage until the server is idle and has time to write data
to the hard disk.

A cache is not the same as a RAM disk.  A RAM disk looks like a disk
to a user or a program; it contains files and directories.  A cache is
not visible to a program, and usually only contains pieces of files
and directories.  A RAM disk emulates a hard disk, but never actually
writes the data onto a disk.  Instructions for installing and using
the cache program are covered later in this document.

You need to decide how big to make your disk cache and whether you
want the disk cache to be started each time you start 3+Open OS/2 on
your server.

By default, the 3+Open LAN Manager installation program automatically
installs the cache program so that it is started with a cache enabled.
The size of the cache is automatically determined based on the total
system memory in the server.  To do this, the installation program
modifies your CONFIG.OS2 file by adding a disk cache command to set
disk caching options.

The maximum value of cache that NETSETUP can establish is 640 KB.  A
significant performance increase can be attained by increasing this
value.  If your system has more than the minimum 4 MB of RAM, set this
value to 2048 KB or higher.

To change the size of cache, edit the CONFIG.OS2 file and change the
line:

diskcache = 640

to

diskcache = 2048

The CONFIG.OS2 file is found on server drive C:/.

For more information about using the disk cache command in your
CONFIG.OS2 file, see Chapter 2 of the Microsoft Operating System/2
Setup Guide.

.BR;Preparing for Installation
.BR;Follow the procedures in the 3+Open for 3Servers Installation and
Setup Guide  and the 3+Backup Guide to prepare your server for the
installation of 3+Open system software.

Changes to the 3+Open OS/2 Utilities
CHKDSK can be run on the server using the NETRUN command.  Cache must
be off to run CHKDSK.  From an OS/2 client, type:

NET USE drive: \\server name\sharename

drive:

NETRUN CACHE /STOP

NETRUN CHKDSK server drive:

The server drive is the logical volume, such as D, E, or F, on the
server, not the linked drive.  Note that running CHKDSK on drive C
will lead to incorrect results due to open system files.  Similarly,
if any files on other drives are open, CHKDSK will also fail on those
drives.

.BR;Operational Characteristics
.BR;The CHKDSK and DIR commands do not agree on the amount of free space
reported.  This is a result of cluster rounding; DIR reports usable
sectors, while CHKDSK reports total sectors.

The cache program allows you to configure, enable, start, and stop the
disk cache.  This program also:

Sets and displays configurable options for the cache
Starts the lazy-write process

To take full advantage of the cache program, you need to know as much
as possible about the disk cache itself.

.BR;Using Disk Caching
.BR;Programmers working with disk caching can take advantage of additional
speed gains by not writing data to the hard disk until some preset
condition exists.  Since the information may have been modified in the
cache during this delay before the save takes place, the operating
system saves time by avoiding at least one trip to the disk.

You can also delay writing to disk until the disk is idle.  The
program does not have to wait until the data is actually transferred
to the disk to continue.  In this case, the program assumes the data
has been written to the hard disk, but the data has only been moved to
RAM.  The information is written to disk later when the data is
flushed from the cache.  (Flushing is the process of writing cached
data to disk.)  This is known as lazy-write caching.

Caching provides improved performance but requires careful management.
If you need to turn the server's power off, be sure all cached data
has been written to disk.  Otherwise, data written to the cache can be
lost.  You must manually flush the cache, turn off the lazy-write
option, and write data to your hard disk before resetting your server.
To do this, type:

NET USE drive: \\server name\volume

drive:

NETRUN CACHE /STOP

Failure to turn caching off can result in corrupted disk information.

It is highly recommended that an uninterruptable power source be used
 when lazy-write is enabled.  An unexpected power outage can otherwise
 result in corrupted disk data.  Since cache information is not
 written to the drive until later, an unexpected
 outage can result in inconsistent disk data.

NOTE:  You can only enable this cache program on an entire physical
disk.  You cannot enable caching or the lazy-write option on
individual partitions.

If for some reason your server stopped with information still in the
cache, type the following command to try to recover files that may
have been partially written to the cache:

NETRUN CHKDSK server drive: /F

Using the Cache Program
To run the cache control program from an OS/2 client, link to a volume
on the 3+Open server.  Type:

NET USE drive: \\server name\volume

drive:

NETRUN CACHE /parameter

For example, you can type:

NETRUN CACHE /OPTIONS

to see which parameters are currently selected for the cache.  A
report similar to the following appears on your screen:

Cache Options
-------------------------------------------------
Status    Stopped
Cache Size (Kbytes)  256
Drive C is ENABLED with Write Through selected.
Drive D is ENABLED with Lazy Write selected.

NOTE:  The drive letters in the screen indicate physical drives,
rather than logical drives.  Drive C is the first physical drive,
drive D is the second physical drive, and so on.  These are not the
same as drive volumes C, D, or E, recognized by the
operating system.  Up to 14 physical drives can be cached.

You can modify options for your server's cache by using the cache
command.  The cache command must be typed with one or more options
using the following syntax:

NETRUN CACHE /parameters

The following parameters are available.

Parameters   Purpose

start        Start or restart cache with a new configuration.

size:n       Where n is the total size of the cache in kilobytes.
             (The cache may be from  64 to 7200 kilobytes.)
             This option overrides the disk cache entry in the
             CONFIG.SYS file.

cache[:drive:[on|off]]
             Enable or disable cache for specified disk.  Using an *
             indicates all physical drives.

lazy[:drive[on|off]]
             Enable or disable lazy write on the drive(s) specified.
             Using an *indicates all physical drives.

stop         Stop the cache and flush the contents of the buffer.

options      Display current configuration options.

stats[:c|u]] Display cache statistics

Help         Displays additional information on the options in this
             menu.

Parameters are processed in the order they appear on the command line.
If the order of the options causes any errors, the program will exit
with the cache stopped.

If you want information about the command syntax for the cache
command, type:

NETRUN CACHE /HELP

.BR;Comments
.BR;Disk caching is started by default each time you start 3+Open OS/2.
If you do not want to have the cache start automatically at boot time,
you can use the cache program to start disk caching whenever you want
to.

For best results, start the cache before you run other programs.  Each
program that runs requires a certain amount of memory.  As more
programs run on the server, memory becomes more fragmented.  The
cache program has difficulty finding and reserving a large piece of
contiguous memory, so the cache may be smaller than desired.

The /start and /stop parameters are provided to explicitly start and
stop the cache; they are not required to reconfigure the cache.  When
you reconfigure the cache, the new configuration is stored in memory
until the last parameter is processed.  The cache is then
automatically stopped, reconfigured, and restarted.

Specify the /size, /cache, and /lazy parameters to stop and restart
the cache.

Stopping the cache completely flushes the contents of the cache
buffer.  This is necessary if the cache options are to be changed.
Disk caching stops after all the data has been flushed from the cache.

The /size parameter specifies the amount of memory the cache will use.
In general, increasing the cache size increases the speed of your
system.

The /cache parameter allows you to select caching to occur on
specified drives.  In a multidrive system, the drives can be enabled
independently.  The drive variable can be C, D, E, and so on.  Drive C
names the first physical hard drive, including a
ll of its partitions.  Drive D names the second physical hard drive
and its partitions.  You can use an * in the command line to indicate
all physical drives.

The /lazy parameter enables the write-behind feature of the cache for
the specified disk.  Write-behind is a feature that allows writes to
the disk to be cached in a similar manner as reads.  When lazy write
has been specified for a drive, the cache
program executes a write-behind process for that drive.

NOTE:  The lazy write option must be off to run most disk utilities,
such as CHKDSK.

The /options parameter displays the current configuration of the
cache.

The /stats parameter displays the cache statistics.  The c option
clears the current statistics and resets all values to 0.  The u
option causes the display to update approximately once per second.

The /stats parameter displays a report similar to the following on
your screen:

Cache Statistics For Server \\server name
_________________________________________________

Read Requests-xxxxxxx Disk Reads   -xxxxxxx

Write Request-xxxxxxx Disk Writes   -xxxxxxx
Lazy Write Bypass  -xxxxxxx
Lazy Write Flushes -xxxxxxx

Cache Hits   -xxxxxxx Lazy Write Errors Disk C-0
Lazy Write Errors Disk C-0

This report shows the following information:

Field   Describes

Read Requests The number of read requests that entered the cache.

Disk Reads  The number of physical read requests that the cache sent
down to the disk driver.

Write Requests The number of write requests that entered the cache.

Disk Writes  The number of physical write requests the cache sent down
to the disk driver.

Lazy Write Bypass The number of times a write request bypassed the
cache and went directly to disk.

Lazy Write Flushes The number of writes carried out by the write-
behind process(es).

Cache Hits  The percentage of times a requested sector was in the
cache.

Lazy Write Errors The number of times the write-behind process
encountered a bad sector on the disk during a flush.

The cache program displays an error code if:

The drive number specified is invalid

An invalid option combination is used

An invalid cache combination is used

LAN Manager is not started when you try to start the cache