DATMAN TECHNICAL BULLETIN #007
From: Kan Yabumoto email@example.com
To: DATMAN user
Subject: DATMAN FAQ (Frequently Asked Questions)
Q: Does DATMAN run under Windows 95/98?
A: Yes. The latest addition to the DATMAN family is DATMAN-99 which
is a fully 32-bit driver specifically written for Windows 95/98.
It does not run under any other operating system.
The original DATMAN which was introduced back in 1994 was
written for MS-DOS. It has evolved to the current DATMAN-DOS
1.20.x which is still a real mode driver (TSR).
Q: Does DATMAN-DOS run under Windows 95/98
A: Yes. Since Windows 95/98 is backward compatible, you can run
DATMAN-DOS with Windows 95/98. Now, Windows 95/98 has two types
of DOS-like environments. The first one is the true real mode
environment (DOS 7.0 or 7.1) which exists on every Windows 95/98
system when the system is booted up and being initialized by
processing CONFIG.SYS and/or executing AUTOEXEC.BAT. At that
time, you can run DATMAN-DOS to install itself. If you prevent
the system from entering the Win32 environment (the GUI world
of Windows 95/98), then, the system ends up in the so-called
Command Prompt mode. This is basically a DOS 7.x environment
and no 32-bit applications can execute.
The second DOS-like environment is the so-called DOS Box after
Windows 95/98 has initialized for the Graphic User Interface.
(But it is a Win32 environment and is not technically a real-mode
environment, therefore, the commonly used term, DOS-Box is not
entirely accurate.) At any rate, You can load DATMAN-DOS in either
of the DOS-like environments.
Q: Does DATMAN-DOS behave the same in the two DOS-like environments.
A: No. If you run DATMAN-DOS before the system enters Win32 (GUI),
the DATMAN drive letter is visible and accessible from anywhere
inside Windows 95/98.
On the other hand if you run DATMAN-DOS from a DOS Box, then,
the DATMAN volume's presence is confined to the DOS Box only.
The advantage is that when the DOS Box crashes, (or DATMAN-DOS
gets into trouble), you can just kill the whole DOS box by
the Ctrl-Alt-Del keys and you can start it all over again.
But, this type of operations are tricky at best and we do not
recommend to anybody.
Q: Does DATMAN run under Windows NT?
A: No. None of the DATMAN software (DATMAN-DOS, or DATMAN-99) runs
under Windows NT. However, we are planning to release a
Windows NT-compatible DATMAN software in the future.
Q: Does DATMAN run under Windows 2000?
A: No. Again, Windows 2000 is a whole new ball game to many driver
developers. We are currently working with a new version which
can run under Windows 2000.
Q: When will DATMAN for Windows 2000 becomes available?
A: We don't know. When it comes to developing a new technology which
even Microsoft cannot provide, it takes hard work and lots of
sleepless nights for a company like ours. We do not even give
anybody a "best estimate" of release date. We just can't tell
you until we are finished with the last fatal bug. Some subtle
bug may take months to remove. True.
Q: Does DATMAN-99 use the same tape format as DATMAN-DOS?
A: No. The new long filename support forced to expand the format
to accommodate the new longer filename (in Unicode) format and
other file attributes including much finer filetime information.
However, DATMAN-99 can read old DATMAN-DOS format. In addition,
DATMAN-99 comes with a new updated DATMAN-DOS version which can
read the new DATMAN-99 tape format even in real mode.
Q: I use Windows 95/98 all the time and I don't care about DOS.
Do I ever need DATMAN-DOS?
A: Yes. You should keep DATMAN-DOS around even if your main
operating system is Windows 95/98. That is because when your
hard disk crashes and you use the "boot diskette" provided by
Windows 95/98, all you get is the real mode DOS 7.x world.
That is the time when you need DATMAN-DOS which allows you to read
the tapes you made using DATMAN-99. DATMAN-DOS can access DATMAN-99
tapes in Read-Only mode. The files DATMAN-DOS reads from
DATMAN-99 tapes are restored with short names only. This is
analogous to writing a floppy disk with files with longname
in Win95/98 and later reading the files in DOS. DATMAN comes
with a utility (DCOPY32) to restore long filenames later.
Q: How do you recover files on a tape saved in DATMAN-99 after a
disaster using only the boot diskette and the tape?
A: The standard DATMAN-99 package includes new DATMAN-DOS version
unless you order a special DOS-only package. The DATMAN-DOS
component allows you to operate in real mode (DOS-7.x) environment.
The system will be rebuilt in two steps.
1. Using the boot diskette, boot up the system into DOS 7.x
first and run DATMANFE.EXE (the real-mode DATMAN File Engine)
which can read your DATMAN-99 tapes. The first step is to
copy only the essential files necessary to start Win95
(files in the root directory and \Windows directory and
DATMAN-99 related files).
2. Once a minimal Windows 95 is restored, run DATMAN-99 in
in Win32 mode and restore all the remaining files from the
Q: What is the access time of DATMAN?
A: Well, it's hard to say. That's because, the "access time"
used in other contexts such as DRAM speed, or even hard disk
or CD-ROM access time are not directly applicable to the tape
technology. The throughput measured in terms of MB/min for
relatively large scale file transfer operations is more
realistic number for comparison between tape backup programs
and among the various storage technologies.
DATMAN can achieve 15-40 MB/min. depending on how fast your system
is. Since DATMAN is relatively CPU-intensive software, the
CPU speed does play a significant role in the performance. Also,
there is some fixed amount of overhead for opening and closing
a file. Also, the more files in a directory, the more overhead for
creating a file (e.g., it takes some CPU time to ensure the filename
is unique within the directory). On the average, DATMAN routinely
achieves 15 MB/min for write operation, slightly less for read
operation. The rule of thumb is 1.0 - 2.5 GB/hr.
Q: Is it possible to boot the system directly from the DATMAN tape?
A: No. One way or another, a bootable drive, let it be the diskette,
hard disk, or CD-ROM, must be supported by the BIOS ROM on the
motherboard. So far we have not seen any tape format being a
true standard without which the BIOS can never support it.
Q: I always forget to remove the cartridge from the drive before
turning off my computer. Is this practice dangerous in any way
to my data on the tape?
A: We have seen some backup software's preference of ending a backup
session by always ejecting the tape from the drive. DATMAN does
not care one way or the other. This practice does not endanger the
contents on the tape. It might be very convenient to keep your
regular daily-backup tape on the drive semi-permanently. However,
if you form a habit of ejecting the tape whenever you write
something on the tape, the drive will have an opportunity to update
the operational statistics related to the particular cartridge near
the beginning of the tape which allows DATMAN to analyze the tape
performance especially on the various error rates.
Q: What happens when you lose the power to the tape and/or to the
host PC while DATMAN is writing to the tape?
A: When you run DATMAN the next time, it will recognize that the last
session was abruptly terminated. Typically, it will mount the volume
using the catalog which was written before the last session which
was not properly terminated. Since the newest files written during
the aborted session were not referenced in the catalog, those files
will be absent from the directory. But, DATMAN will display a
warning indicating that abnormal situation and advise you to run
a repair operation. DATMAN can repair such a corrupted tape by
scanning the tape to reconstruct the final state of the catalog which
was not recorded on the tape due to the abnormal termination of the
last session. This procedure is included in the on-line tutorial
and we recommend all DATMAN users to learn this technique.
Q: I have an digital audio tape (the real DAT, not the DDS). Can I
retrieve or record audio data on the tape using your DATMAN software?
A: No. Most DDS drives available on the market do not have the
feature to access the raw audio format and therefore, DATMAN is
not capable of accessing the raw audio data. There are a few
drives which have some capabilities of audio data access. The
DDS drive marketed by SGI (manufacturered by Seagate/Archive an
OEM version of a Python model with special firmware) has such
capability. The difference between an ordinary Python drive and
the SGI model is presumably only the firmware. But, we do not
have more details. Another case is a technology called DDS-DA
by a British based company. Their model is said to be a hybrid
of the DDS and audio-verion DAT. Again, DATMAN does not support
these audio-related functions and please do not ask us any more
details. DATMAN is really a file system which happens to support
the DDS drive. Althouth the DDS drive was derived from the DAT
technology, the SCSI command set that DATMAN interacts with the
tape drive resemble the traditional streamer tape model than the
audio drive which has no SCSI command set.
The following tape drives are DAT models which are audio only and
therefore, not compatible with DATMAN:
Sony TCD-Dx, PCM70x0, PCMRx00, PCMxx, DTC-x000,
Tascam DA-20, DA-30, DA-40, DA-78, DA-xx,
Q: When I delete a file, I do not see any increase in the remaining
space in the DATMAN volume. Is there any way to really delete it?
A: With DATMAN, basically, you cannot reclaim the space once occupied
by a file by deleting it. DATMAN only allows you to "logically"
delete a file but the file will remain on tape. This limitation
comes from the way how almost all tape drives are designed and
DATMAN cannot overwrite at an arbitrary position of tape without
affecting existing data beyond the position. The only ways to
reclaim space on the tape is to either format the entire tape
(you lose everything), or cut off existing data from the furthest
end (please study the PURGE command). The plus side of this
characteristics is that DATMAN allows you to locate and undelete
files even after you delete it. Now, you know why all tape backup
programs give you so little choice (either append the new data
at the end, or overwrite from the beginning). We all have to live
with the way tape storage operates.