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The A, B, C of NICE95: Drive-letters Assignment

Miguel Marquina and Hannes Schwarzbauer - IT/User Support

Introduction

It is not uncommon for knowledgeable PC users to run into conflicts (with NICE) when using local devices attached to their PCs. The ground for such problems is the preassignment of drive-letters that the NICE setup does in order to ensure proper functioning of the system. This article intends to shed some light onto this.

Which drive-letters are reserved by my PC?

A PC "out of the CERN box" has the following drive-letters already (pre)assigned:

A,B (floppies; B is rarely used except if the user asks for a 5.25" drive installed)
C (for a hard disk up to 2GB; also D for larger disks, see below)
E (CD-ROM)

In fact the situation is slightly more complex. Currently hard disks larger than 2GB have to be split in several segments in order to be accessible by the operating system. This is due to a limitation in the ability of Windows 95 (up to OSR1) to address more than 2GB of space (see article elsewhere in this issue). It is no longer an issue with Windows 95 OSR2, Windows 98 or NT, in which case it is enough to address the local disk as a single partition in C:.

Incidentally this is the reason that PCs delivered by the PC Desktop unit have installed 4GB hard disks (and not larger).

Thus D,E,F can be used to map additional partitions, CD-ROMs or external drives and actually they are usually mapped automatically by the system in this case, but they can be changed.

Which drive-letters are reserved by NICE?

When a user with login ID "login-id" accesses the standard NICE environment, the following drive-letters are engaged:

G ( common area for all users sharing with "login-id" disk space in a NICE home server)
J (user home directory; it is equivalent to G:\home\login-id although the mapping is made independently)
P (AFS root, when it is made publicly available)
X,W,Z (NICE volumes)

In addition each division has a divisional volume, usually mapped as the L: drive, but it may be different (K: or M:). Some groups have special letters of their own for special uses (O:, P:, Q: most of the times), but it is the responsibility of the local administrators to check for conflicts.

All these drives are labelled under the generic title "Network Connection" when one opens "My Computer". When the system doesn't find the home directory server (to be mapped to G:), it assumes that the connection is in "stand-alone" mode; it maps G:, J:,etc, to C:\temphome. In that case all the drives are labelled as "Local Disk".

What kind of problems could I expect? - A case study

If you have a standard "NICE PC" and stick to it then the drive-letter assignment is made dynamically to accommodate your hard disk partition(s) and CD-ROM. But the moment you install yourself extra units (Jaz, Zip, CD-Writer, etc) you have to be very careful in the drive-letter re-arrangement you may need to keep a working system.

Let us take as an example the case of a user who had his 4GB disk partitioned in three segments: C: (2GB), D: (1GB) and E: (1GB). The system was assigning dynamically F: for his CD-ROM.

Then he added a Jaz drive. Windows 95 granted G: to the new device, thus stealing this drive-letter from the standard NICE assignments. From that moment on the user was not able to access his NICE files in the "standard" way (through the J: drive). Even though he could see his NICE files by accessing his home directory through the NICE Phone Book:

Search for "login-id" - Click "More Info" - Click "Map Home Directory"

NICE has assumed that the failure to set "G:" implies a stand-alone connection even though the access to the network is working fine.

How to re-assign a drive-letter to a device?

The problem described above and others of similar nature can be easily fixed by reassigning a drive-letter to the device causing the conflict, leaving G: for exclusive usage by NICE. In the case in study it would have been enough to assign H: or later to the Jaz drive (or the internal CD-ROM).

In order to do this you proceed by opening:

Start Menu -> Settings -> Control Panel

Launch the "System" control panel and select the "Device Manager" tab. Open the device whose drive-letter you want to modify, and select the "Settings" tab in the new open window. The second half of the screen presents "Reserved Drive Letters". Just choose the

"Start Drive 
Letter"

(e.g. H:) and eventually the "End Drive Letter" if you would like Windows 95 to dynamically assign it. After closing the panels you would just need to restart the PC for the new settings to take effect.

For matters related to this article please contact the author.

Cnl.Editor@cern.ch