Re: USB memory keys -- the plot thickens
- From: Lon Hooker <ganchero@xxxxxxx>
- Date: Thu, 04 May 2006 02:31:23 -0700
I'm a bit late to this thread (just now joined the group) so if I go over any ground already covered, forgive me.
First, in order for removables to be used by an LVM system, there are a few simple rules:
o ALL USB magnetic media is "partitionable"... no exceptions. This specifically includes the so-called "Large Floppies".
o All USB removables must contain a valid partition table and be "blessed" by LVM, such "blessing" to take the form of a "drive letter allocation table", or DLAT. There is one exception...
o That exception is the "Large Floppy". It is defined as UNpartitioned media having a FAT16 format. No partition table, no DLAT. Like the familiar standard floppy, it is accessed directly by the OS and requires no drivers beyond those needed by its hardware (the USB stack in this case)
o ALL partitionable media is supported and controlled by the "USBMSD.ADD /REMOVABLES:n" statement in config.sys. Again, this specifically includes "Large Floppies".
Previously I had reported no joy getting an IBM 512 MB USB memory key
to work on my MCP2 FixPak5 system, even with the latest USB drivers.
A USB floppy drive works. A USB CD-ROM drive works. A device with a
2 GB Compact Flash card connected via USB works. But the memory key
did not work, even though Windows XP had no problem with it, and
identifies it as being formatted FAT16, which should be compatible
Good. This says your USB sub-system is correctly installed... hopefully with the latest USB stack, 10.162 being the latest, although 10.157 is acceptable (those are the ones available to eCS... I have no idea what is available for your MCP2 system). Older versions do have problems.
So yesterday I spent a few bucks on a CompUSA 128 MB USB memory key to
use as a test. Inserted it in my system, and it worked right off the
No surprise... it's a "large floppy".
So, question #1, why would a CompUSA 128 MB memory key work but not an
IBM 512 MB memory key? The readme that accompanied the USB drivers did
mention that the drivers wouldn't work with a tiny IBM memory key (I
think it was 16 MB or less), but that doesn't apply to this situation.
But the oddities didn't end there. When I inserted the IBM memory key
into the system, the Removable Device Monitor would dutifully report
that drive F: had been attached to the system, but no icon would appear
in the Drives folder, and no drive F: would appear in LVM's logical view.
LVM would show the memory key in the physical view, reporting 499 MB of
free space, which is approximately the right size for that memory key.
Apparently your IBM key is partitioned (i.e. has a partition table), but has NOT been blessed by LVM. The USB system recognizes and attaches the device, but LVM can't find a DLAT, so ignores it. Even worse, LVM can do nothing to change things. If you do try to create a partition, LVM tells you the freespace is unusable and does nothing. So you're in a bind: To see the drive, you have to change it, but you can't change it because LVM can't see it. :-(
After much trial-and-error, I found that the only consistently reliable way to configure USB removables is with DFSee. It understands LVM, can easily create a usable partition and even "bless" it with a new DLAT. The only task remaining is to install a file system, and the current version (8.00) can even do that (for FAT16/32 only).
Speaking of partitioning tools... NEVER, EVER, let either PQMagic or W$ touch a disk that will be used by LVM... they do really bad things to the geometry. :-(
With the CompUSA memory key, however, the Removable Device Monitor would
dutifully report that drive F: had been attached to the system, and an
icon would appear in the Drives folder. Yet LVM did not show any F:
drive in the logical view, and the physical view reported a drive with
only 31 MB of total and free space. Meanwhile, a directory listing in a
command window showed the correct amount of space (128 MB) on the drive.
So, question #2? Why can't LVM see what the command line sees? I'm
using the latest LVM code as well.
Again, no surprises. Per the rules, LVM's role is limited here. Because the system accesses "Large Floppies" directly, LVM has no function beyond passing them to os2dasd.dmd for generic drive letter assignment. As for the command line, it uses system calls for drive space so never looks to LVM at all.
In LVM's view, since there is no DLAT, the disk simply "isn't there". What you see when you open it are a number of "dummy" containers, or placeholders, equal to what you specified in "/REMOVABLES:n", but they're useful only when a properly configured device is attached. IOW, ignore LVM when dealing with large floppies... it's not only blind, it lies!
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