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Super Virtual Disk
Swappable/Lockable/Removable Virtual Disk
for OS/2
SVDISK
Version 1.01
07/08/94
TABLE OF CONTENTS
_________________________________________________________________
1.0. INTRODUCTION TO Super Virtual Disk ..................3
1.1. What is Super Virtual Disk? ....................3
1.2. Features of SVDisk .............................3
2.0. SYSTEM REQUIREMENTS .................................4
3.0. COPYRIGHT NOTICE ....................................4
4.0. WARRANTY ............................................4
5.0. COST OF Super Virtual Disk ..........................4
6.0. CONTENTS OF THIS PACKAGE ............................5
7.0. INSTALLATION ........................................6
7.1. Quick start ....................................6
7.2. SVDisk.sys parameters ..........................7
8.0. CONTROLLING Super Virtual Disk ......................8
8.1. Super Virtual Disk Control (SVDC.EXE) help
screen ..............................................8
8.2. Options for SVDC ...............................9
8.3. PM Super Virtual Disk Control ..................11
8.4. Diskette boot bypass using VFloppy .............11
9.0. PROGRAMMING INFORMATION .............................11
10.0. EXAMPLES ...........................................13
10.1. Example 1: Locking non-swappable memory and
querying status .....................................13
10.2. Example 2: Ejecting virtual media .............13
10.3. Example 3: Reconfiguring VFloppy device .......14
10.4. Example 4: Inserting virtual media ............14
10.5. Example 5: Multiple operations ................14
11.0. ERROR MESSAGES .....................................15
11.1. List of error messages ........................15
2
1.0. INTRODUCTION TO Super Virtual Disk
_________________________________________________________________
1.1. What is Super Virtual Disk?
Super Virtual Disk (SVDisk) is a 32-bit OS/2 device driver that
emulates either a removable Virtual Disk (VDisk) or a removable
Virtual Floppy (VFloppy) drive. By using OS/2's virtual memory
management facility, SVDisk allows the entire contents of the
disk to be swapped out via the paging mechanism. If the SVDisk
is frequently accessed, OS/2 will keep the most recently used
memory pages in RAM, and SVDisk will essentially behave like a
RAM Disk.
1.2. Features of SVDisk
- Emulates multiple VDisk devices up to 16MB each even on a 4MB
system. Cluster size is maintained at 512 bytes by varying
the size of the File Allocation Table (FAT) to reduce file
slack.
- Emulates multiple VFloppy devices, ranging from 360KB to
2.88MB. Virtual media support ranges from 160KB to 1.2MB for
5.25" VFloppy device, and from 720K to 2.88MB for 3.5" VFloppy
device. If the VFloppy is a 3.5" device, automatic media
sensing is supported.
- Media in SVDisk is removable. This allows SVDisk to release
all memory used by the device back to the system.
- Dynamic device reconfiguration is supported for the VFloppy
device. If you load a 1.44MB VFloppy device, it can be
reconfigured later (without rebooting) as a 360KB, 720KB,
1.2MB or 1.44MB drive.
- Special boot sector on VFloppy device to allow bypassing of
floppy boot if the image of the VFloppy is transferred to the
a real diskette using DISKCOPY.
- Formatting and sector/track read/write are supported.
- SVDisk allows locking of swappable memory into non-swappable
memory. Once memory is locked, SVDisk will behave like a RAM
drive without paging delay. The size of the lock can be
specified by the user, since locking the entire disk as non-
swappable can have serious performance impact to OS/2's
virtual memory operation.
- A 32-bit command line utility and a 32-bit PM application are
included to provide complete control of all the capabilities
of SVDisk.
3
2.0. SYSTEM REQUIREMENTS
_________________________________________________________________
Machines equipped with an Intel 386SX compatible or higher
processor. OS/2 2.1 or higher, with minimum 4MB of memory.
3.0. COPYRIGHT NOTICE
_________________________________________________________________
SVDisk (Super Virtual Disk) Version 1.01 07/08/94
(c) Copyright 1994 by Albert J. Shan. All Rights Reserved.
No part of this program may be disassembled, modified or altered
by any means.
4.0. WARRANTY
_________________________________________________________________
I, Albert J. Shan, make no warranties, expressed or implied,
including, but not limited to, merchantability or fitness for any
particular purpose. In no event shall Albert J. Shan be liable
for indirect or consequential damages arising from the use of the
software program.
You are free to redistribute this shareware package in its
entirety. No part of this package may be included as part of a
commercial package. If you have any questions about commercial
distribution of Super Virtual Disk, I can be contacted at:
Albert J. Shan
4620 Granville Avenue
Richmond, B.C.
CANADA V7C 1E4
or via CompuServe, ID 70730,401
or via Internet, 70730.401@compuserve.com
5.0. COST OF Super Virtual Disk
_________________________________________________________________
The user is granted a 30 days trial period, after which he or she
is required to register the product. The cost of a single
machine license is $30 U.S. Please refer to the file ORDER.FRM
for details.
4
6.0. CONTENTS OF THIS PACKAGE
_________________________________________________________________
The following files are included in this package:
SVDISK.SYS - Super Virtual Disk device driver
SVDC.EXE - Super Virtual Disk Control
PMSVDC.EXE - PM version of SVDC
SVDISK.DOC - This documentation
SVDISK.HST - History of SVDisk
ORDER.FRM - Order form
README - Last minute information
5
7.0. INSTALLATION
_________________________________________________________________
7.1. Quick start
To install SVDisk, make a subdirectory called SVDISK, and copy
all the SVDisk files into \SVDISK. Then edit your OS/2
CONFIG.SYS to include a line:
DEVICE=D:\SVDISK\SVDISK.SYS
Where D: is the drive where you created the SVDISK subdirectory.
You may want to add SVDISK to the path by appending D:\SVDISK at
the end of the PATH= statement in CONFIG.SYS.
When you load SVDisk without any parameter as in the above
example, it will create a 1.44MB VFloppy device after you reboot
the system.
When SVDisk is loaded, it does not put a media in the virtual
drive. You have to manually insert it with SVDC or PMSVDC. To
insert a virtual media after the system is booted, you type:
SVDC X: /i:720
Where X: is the drive letter of the SVDisk after boot.
This will insert a 720KB virtual media into the drive. If you
specify /i without any parameter, SVDC will insert a media with
the maximum capacity as defined by the SVDisk.sys device in
CONFIG.SYS. To make media insertion automatic, simply edit
STARTUP.CMD on your OS/2 boot drive and add the SVDC line to it.
Alternatively, you can insert the virtual media by using the
CALL= statement in CONFIG.SYS:
CALL=D:\SVDISK\SVDC.EXE X: /i:720
If you want to install a 8MB VDisk type device, edit your
CONFIG.SYS by adding a line:
DEVICE=D:\SVDISK\SVDISK 8192 512
This will create a 8MB VDisk device with 512 root directory
entries after you reboot the system.
6
7.2. SVDisk.sys parameters
SVDisk.sys can be loaded with no parameter to up to two
parameters. To load SVDisk as a VFloppy device, you must specify
the size of the VFloppy device in KB. For example:
REM *** Load a 1.44MB VFloppy device ***
DEVICE=\SVDISK\SVDISK.SYS 1440
REM *** Load a 2.88MB VFloppy device ***
DEVICE=\SVDISK\SVDISK.SYS 2880
REM *** Load a 360KB VFloppy device ***
DEVICE=\SVDISK\SVDISK.SYS 360
The possible values for VFloppy device are: 360, 720, 1200, 1440,
and 2880. Since SVDisk defaults to a 1.44MB VFloppy device, the
1440 parameter can be omitted.
To load SVDisk as a VDisk device, you can specify up to two
parameters:
DEVICE=\SVDISK\SVDISK.SYS ssss eeee
Where ssss is the size of the VDisk device, and eeee is the root
directory entries for the device. eeee is optional, and if you
do not specify it, SVDisk will default to 64 root directory
entries.
The possible values for ssss are from 16 to 16384 (16KB to 16MB.)
The VDisk device will always round up the size into 16KB
boundary. If you specify a 250KB VDisk device, it will be loaded
as 256KB.
The possible values for eeee are from 16 to 1024. This value is
also rounded up in multiple of 16.
If you load a VDisk device near the size of 4MB, it will attempt
to resolve the File Allocation Table (FAT) size as either 12-bit
or 16-bit. In the case of conflict due to a large root directory
entries specification, SVDisk will slightly reduce the VDisk size
in favor of a 12-bit FAT for lower disk sector overhead in the
system area on the virtual media.
SVDisk distinguishes a VDisk device from a VFloppy device solely
by the ssss (size) parameter. If ssss is one of the possible
values for a VFloppy device, it will load itself as a VFloppy
device, and the second parameter is ignored.
7
8.0. CONTROLLING Super Virtual Disk
_________________________________________________________________
Two programs are provided to control the SVDisks: SVDC.EXE and
PMSVDC.EXE. PMSVDC.EXE is the Presentation Manager version of
SVDC.EXE.
8.1. Super Virtual Disk Control (SVDC.EXE) help screen
Type SVDC at the OS/2 command prompt to receive this help screen:
Super Virtual Disk Control (32-bit) Version 1.01 SHAREWARE VERSION
(c) Copyright 1994 Albert J. Shan. All Rights Reserved.
For use with Super Virtual Disk driver (SVDISK.SYS)
Usage: SVDC [options] Drive:
[options] /c Fake a disk change.
/e[f] Eject media [f = forced eject].
/i[:size] Insert media (if size is not specified, default
to max. drive capacity.) Size can only be
specified for the VFloppy device. Valid sizes are:
160, 180, 320, 360, 720, 1.2, 1.44, 2.88.
/l:size Lock SVDisk in non-swappable memory. Size
is anywhere from 0 (KB) to the max. media size.
/q Query SVDisk status
/r[:size] Reconfigure VFloppy device capacity (if size is not
specified, default to max. drive capacity.) Valid
sizes are: 360, 720, 1.2, 1.44, 2.88.
/u Unlock non-swappable memory used by the SVDisk.
Drive: Drive letter of the Super Virtual Disk.
NOTE: The drive must not contain any media before reconfiguring with /r.
*** Note: parameters within [] are optional.
If you specify the drive letter of a SVDisk and without
specifying any other options, SVDC will report the current status
of the SVDisk drive as if the Query Status switch (/q) is
specified. For example:
[C:\SVDISK]svdc j:
SVDISK.SYS Version: 1.01
Reconfigurable device size: 2.88MB
Current device size: 2.88MB
Current media size: 1.44MB
Non-swappable memory locked: 128KB
8
8.2. Options for SVDC
/c Fake a disk change. This command will cause the SVDisk
specified to appear as if it has been changed (ejected
then reinserted.) This is accomplished by changing the
Volume Serial on the SVDisk. If the program in
question is looking for a change in Volume Label or a
DOS program is looking for a change line bit in
hardware, /c will not work.
/e[f] Eject media. This will eject the media in the SVDisk,
thereby releasing all memory, including locked memory
(see /l and /u below) back to the system. If a program
is currently running off the SVDisk, you must specify
/ef to force the disk to eject. Further access to the
SVDisk drive will cause a drive not ready error.
/i[:size] Insert media. If size is not specified, it will insert
a media with the exactly same size as the SVDisk
device. For example, if the VFloppy is 2.88MB,
specifying /i alone will insert a 2.88MB media into the
SVDisk drive. The optional size parameter is only
applicable for a VFloppy device. This allows different
size media to be inserted into the VFloppy drive. If
the VFloppy is a 5.25" 360KB device, the possible
values are: 160, 180, 320, and 360. If the VFloppy is
a 3.5" 1.44MB device, the possible values are: 720 and
1.44. Depending on the type of VFloppy device, the
possible values are: 160, 180, 320, 360, 720, 1.2, 1.44
and 2.88.
/l:size Lock virtual disk in non-swappable memory. This will
cause the virtual memory allocated by SVDisk to be
locked in real memory pages, and they will be precluded
from swapping out by the system. The starting location
of the lock is fixed at the beginning of the disk, at
logical sector 0. The size parameter is anywhere from
0 to the maximum size of the media in the SVDisk. It
will be rounded up in 4KB in size as OS/2 can only lock
memory in page boundary. A size of 0 is equivalent to
unlocking all the memory (see /u switch below.) If a
lock already exists on the SVDisk, it will be released,
and the new lock size will be installed. If there is
not enough real memory for the lock, /l will fail, and
at the same time, releasing any memory previously
locked.
The OS/2 kernel will swap out other processes in order
to make room for the lock. This may take a while as
pages are being swapped out. The system will not be
responsive when the kernel is into heavy paging
activities.
9
WARNING: Locking memory as non-swappable has the same
effect as removing system memory on the hardware level.
If you have a 8MB system, locking a few mega bytes of
memory will make your system appear as if it has 4MB
total system memory or less. If the lock succeeds in
locking large amount of memory, and the remaining non-
swappable memory is extremely low, the OS/2 virtual
memory paging mechanism will thrash. Although the
system is not crashed, it will be paging in and out so
frequently that the system can no longer respond to the
user's input. You will need to press Ctrl-Alt-Del to
recover in this case. In general, it is recommended
not to lock more that one quarter of total system
memory as non-swappable for all SVDisk devices
combined. PMSVDC.EXE will limit the maximum of the
lock to half of total system memory or the maximum disk
size, whichever is less. On the other hand, SVDC.EXE
is designed to be flexible, so any lock size is
possible.
/q Query SVDisk Status. The following is a typical SVDisk
report:
SVDISK.SYS Version: 1.01
Reconfigurable device size: 2.88MB
Current device size: 2.88MB
Current media size: 1.44MB
Non-swappable memory locked: 128KB
/r[:size] Reconfigure VFloppy device capacity. This switch is
only applicable to the VFloppy device. It allows
dynamic device reconfiguration while the system is
running. Before you can reconfigure the VFloppy
device, the media must first be ejected via the /i
switch. Specifying /r alone will reconfigure the
VFloppy device to the maximum capacity as loaded by the
device driver. If SVDisk is loaded as a 1.2MB VFloppy
device, you cannot reconfigure it to a 1.44MB or 2.88MB
VFloppy device. For example, if SVDisk is loaded as a
3.5" 2.88MB VFloppy device, you can reconfigure it to
5.25" 360KB, and 1.2MB VFloppy device. You can also
reconfigure it to 3.5" 720KB, 1.44KB and 2.88MB VFloppy
device.
/u Unlock non-swappable memory used by the SVDisk. This
is the same as specifying /l:0. Locked memory is
released as being swappable.
10
8.3. PM Super Virtual Disk Control
The Presentation Manager version of Super Virtual Disk Control
(PMSVDC.EXE) provides identical functions as SVDC.EXE with one
exception. The lock function will limit the maximum available
memory for the lock as half of total system memory or maximum
media size, whichever is less. This means if you have 16MB of
memory, and your VDisk device is 16MB, the largest memory size
you can lock is 8MB. Many system board reserves up to 384K of
memory for shadow ROM and other purposes. This effectively
reduces your total system memory. Instead of 16MB (16384KB), you
get 16000KB total system under OS/2 and the maximum size for the
lock in this case is 8000KB. The lock function also warns you if
you are locking more than one quarter of the total system memory.
If you have multiple SVDisk devices, PMSVDC will add up all
memory locked all SVDisk devices, subtract the existing lock size
on the current device, then add the new requested size to see if
it exceeds one quarter total memory limit. In general, the total
memory locked by all SVDisk devices should be less than one
quarter of the total system memory to prevent OS/2 pager from
thrashing.
8.4. Diskette boot bypass using VFloppy
SVDisk contains a special boot sector which can be used to bypass
real floppy boot. You can do this by transferring the image of a
VFloppy device with DISKCOPY to a real diskette. If you leave
the diskette in drive A:, upon system reboot, you will get the
following message on the screen:
Transferring system boot from diskette to hard drive...
And the boot sequence will be transferred to the hard drive. If
you have OS/2 Boot Manager installed, you will see the Boot
Manager at this point.
9.0. PROGRAMMING INFORMATION
_________________________________________________________________
When SVDisk is used as a VFloppy device, it tries to emulate a
real floppy drive as much as possible. However, this emulation
is not 100%. If you write a program against the behavior of a
real floppy drive, it will almost certainly work with SVDisk.
The converse is not always true. This is because SVDisk makes
certain assumptions to simplify many of the internal operations
which are true for a virtual device. The common pitfall is to
assume reading and writing to a floppy device are always slower
than other computational threads. If a multithreaded OS/2
application is designed with the above assumption, it will almost
certainly fail because the disk read/write operations are much
faster than the program has expected.
11
SVDisk supports the following IOCtl Category 8 logical disk
commands (in hex):
00 Lock drive
01 Unlock drive
02 Redetermine media
04 Begin format
20 Block removable
21 Query logical map
43 Set device parameters (the changing the BPB of the device is
not supported)
44 Read track
64 Write track
65 Verify track
45 Format and verify track
60 Query media sense
63 Query device parameters
Please refer to OS/2 2.x SDK (Software Development Kit) on
programming the IOCtl interface.
12
10.0. EXAMPLES
_________________________________________________________________
The following examples assume you have the following lines
installed in CONFIG.SYS:
DEVICE=D:\SVDISK\SVDISK.SYS 8192 512
DEVICE=D:\SVDISK\SVDISK.SYS 2880
CALL=D:\SVDISK\SVDC.EXE H: /i
CALL=D:\SVDISK\SVDC.EXE I: /i:1.44
The first SVDisk is an 8MB VDisk device with 512 root directory
entries, with drive letter 'H' assigned to it by OS/2. The
second SVDisk is a 2.88MB VFloppy device, initially loaded with a
1.44MB virtual media, and is assigned as drive 'I'.
10.1. Example 1: Locking non-swappable memory and querying status
You would like to lock the first 600K of SVDisk H: in non-
swappable memory, and query the status at the same time:
SVDC H: /l:600 /q
And you get the following report:
SVDISK.SYS Version: 1.01
Reconfigurable device size: 8192KB
Current device size: 8192KB
Current media size: 8192KB
Non-swappable memory locked: 600KB
10.2. Example 2: Ejecting virtual media
You can eject the virtual media in SVDisk so that all memory used
(including locked memory) is returned to the operating system:
SVDC I: /e
If the SVDisk is in used by a process (ie: a running program,
open files, etc.), you'll receive an error message:
KWT0131: Drive I: is not ready or in use by another process.
You can force eject the virtual media by specifying /ef:
SVDC I: /ef
13
10.3. Example 3: Reconfiguring VFloppy device
You want to change the VFloppy drive I: into a 1.2MB 5.25"
device:
SVDC I: /r:1.2
10.4. Example 4: Inserting virtual media
You want to insert a 360KB virtual media into drive I:, which has
just been reconfigured to a 1.2MB VFloppy drive:
SVDC I: /i:360
10.5. Example 5: Multiple operations
You can combine example 3 and 4 plus locking and querying all in
one step:
SVDC I: /r:1.2 /i:360 /l:180 /q
And you'll receive this status report:
SVDISK.SYS Version: 1.01
Reconfigurable device size: 2.88MB
Current device size: 1.2MB
Current media size: 360KB
Non-swappable memory locked: 180KB
14
11.0. ERROR MESSAGES
_________________________________________________________________
11.1. List of error messages
The following is a list of major error messages returned by
SVDC.EXE. The error return code is also displayed as part of the
prefix in the error message:
SVDnnnn: Error message text
Where nnnn is the error return code.
SVD0016: Drive X: is not a Super Virtual Disk.
SVD0017: SVDISK.SYS has a higher revision level.
SVD0018: Invalid media size.
SVD0020: Unable to eject Super Virtual Disk due to memory deallocation error.
SVD0021: Unable to insert Super Virtual Disk due to memory allocation error.
SVD0022: No media in drive.
SVD0023: You cannot insert two media in the drive.
SVD0024: Incorrect size specified.
SVD0025: System failed to lock memory as non-swappable.
SVD0026: System failed to unlock non-swappable memory.
SVD0027: No non-swappable memory locked by the Super Virtual Disk.
SVD0028: Cannot reconfigure Super Virtual Disk with a media in the Drive.
SVD0029: Only VFloppy type device can be reconfigured.
15