Max PGPdisk volume sizes are determined by 5 things:

• PGP version (6.0.x/6.5.x or 7.x/8.0) -- since PGP imposes
  limits on file systems supported and max size of container
  files on different types of host drives;
   
• Windows version (Win9x/Me vs. WinNT4/Win2K/WinXP)
  -- Windows (in tandem in PGP) constrains the file systems 
  supported as well as the capabilities of the file system;
   
• PGPdisk volume file system (FAT16, FAT32, or NTFS) --
  esp. max volume size, since PGPdisk volumes act like hard 
  drive volumes & Windows must format and use them;
   
• Host drive file system (FAT16, FAT32, or NTFS) -- esp.
  max file size, since PGPdisk volumes are in reality single 
  container files, though max volume size also plays a role
  here, as does PGP's support for container files on different
  host drives;
   
• Host drive size (obviously, you can't create a PGPdisk volume 
  larger than the host drive itself) 

So, here's how it all plays out:

Windows 9x/Me

On PGP 6.0.x/6.5.x, PGPdisk volumes are effectively limited to 2 gb in size. Here's why:

• FAT16 host drives can't be larger than 2 gb (and thus max file size on FAT16 host drives is 2 gb);
   
• While FAT32 host drives can be much larger on Win9x/Me and allow for file sizes of up to 4 gb, 
  PGP won't even create PGPdisk volumes on FAT32 host drives if the PGPdisk volume is larger 
  than 2 gb  -- PGPdisk crashes (even on NT4 and Win2K);
   
• On Win9x/Me, PGPdisk automatically formats volumes with FAT16, which limits the volumes to
  2 gb (and FAT16 volumes are constrained to 2 gb, even on NT4/2K systems). Win9x/Me users don't  
  even get to select the file system for PGPdisk volumes (though WinNT4/Win2K users do). 

PGP effectively won't let you take advantage of FAT32 support in Win9x/Me (and even imposing FAT16-like limits on WinNT4/Win2K).

Bottom line, if you want a PGPdisk volume larger than 2 gb, you'll need an NTFS host drive, -- which Win9x/Me can't give you -- AND you need the ability to format something other than FAT16, which PGP won't let Win9x/Me users do.

2 gb on PGP 6.0.x and 6.5.x appears to be the end of the story for Win9x/Me.

On PGP 7.x and 8.0, PGPdisk volumes are limited to 4 gb. Here's why:

• FAT16 host drives can't be larger than 2 gb  (and thus max file size on FAT16 host drives is 2 gb);
   
• FAT32 host drives can theoretically be as large as 2tb but can only support PGPdisk volumes 
  of 4095 mb -- that's the max file size on FAT32 drives;
   
• FAT16-formatted PGPdisk volumes are limited to 2 gb (even on NT4/2K); 
   
• FAT32-formatted PGPdisk volumes are theoretically capable of much larger sizes, but you can 
  only put the container files on FAT32 host drives on Win9x/Me, which, again, limit the file size 
  of the container to 4095 mb (4gb). 

Bottom line, the largest PGPdisk volume you can create on a Win9x/Me system with PGP 7.x is a FAT32-formatted 4gb (4095mb) PGPdisk volume on a FAT32 host drive. If you're working with FAT16 host drives, then you're limited to 2gb PGPdisk volumes (whether they be formatted FAT16 or FAT32).

Note: PGPdisk from PGP 6.5.8ckt appears to provide more leeway with FAT32 host drives, allowing the max file size to go up to 4095 mb. However, as the CKT builds still don't allow Windows 9x/Me users to choose to format PGPdisk volumes as FAT32, the max volume size is still capped at 2 gb.

Windows NT4/2000

NTFS makes all the difference with Windows NT4/2000 systems.

On PGP 6.0.x/6.5.x, the largest volume PGPdisk will create on FAT16 and FAT32 host drives is 2gb, no matter how you (intend to) format the PGPdisk volume:

• FAT16 host drives can be up to 4gb, but PGPdisk will only create PGPdisk volumes on 
  FAT16 host drives of up to 2gb;
   
• FAT32 host drives can be up to 32gb on Win2K (NT4 can't do FAT32 at all), but PGPdisk 
  still limits PGPdisk volume sizes on FAT32 host drives to 2gb. 

In other words, with FAT16 and FAT32 host drives, PGP imposes Win9x/Me FAT16 type limitations.

With PGP 6.0.x/6.5.x, if you move to NTFS formatted host drives, you can (probably) do FAT32-formatted PGPdisk volumes up to 32gb and NTFS-formatted volumes up to...who knows how large. The limit for NTFS-formatted PGPdisk volumes on NTFS host drives is unknown to me, but is undoubtedly very large (too large to be practically useful, I'd guess). Note:

• NTFS host drives can be unbelievably large (much larger than current hard drives); in effect, the size is unlimited. According to Microsoft: 

           Other Microsoft publications mention creating and/or formatting volumes of 2 to 16 tb. So, the size of
           the NTFS host drives needn't be a problem. 

• Win2K and XP are limited to formatting FAT32 drives up to 32gb -- see:

           32gb is probably the absolute limit for FAT32-formatted PGPdisk volumes on Windows 2000,
           though PGPdisk might impose a smaller limit (I don't know). A FAT32-formatted PGPdisk volume
           of this size would have to go on an NTFS host drive, as the max file size for FAT32 drives is 4 gb.

• The limit on NTFS-formatted PGPdisk volumes on NTFS host drives is, again, unknown to me, but
  likely to be very large. NTFS volumes can be created/formatted between 2 to 16 tb. Moreover, files
  on NTFS host drives can be very large (theoretically up to 16 tb), so the PGPdisk container files can
  also be very large. 

Again, PGPdisk may impose smaller limits on FAT32-formatted and NTFS-formatted PGPdisk volumes residing on NTFS host drives, but I haven't been able to find any mention of them.

On PGP 7.x and 8.0, you get a bit more leeway with FAT16/FAT32 host drives, and the situation with NTFS drives is essentially the same.

• On FAT16 host drives, which are limited to 4gb on NT4/2K, PGPdisk will create PGPdisk volumes 
  up to the limit (and the max file size for FAT16 drives is 4 gb), though if the PGPdisk volumes are 
  greater than 2gb, you'll have to format them FAT32 or NTFS;
   
• On FAT32 host drives, PGPdisk volume sizes are limited to 4gb because of the 4 gb file size limit
  on FAT32 drives, even though FAT32 host drives can go up to 32gb on Win2K (NT4, again, doesn't 
  do FAT32);
   
• On NTFS host drives, the sky's the limit, as with PGP 6.0.x/6.5.x above. If the PGPdisk volume is greater 
  than 2gb, you'll have to format it FAT32/NTFS, as before. 

Strangely, with Windows 2000 on PGP 6.0.0, PGP 6.0.2, and PGP 6.5, it seems you can't format PGPdisk volumes as anything other than NTFS (no matter what the host drive is). PGP isn't officially supported on Windows 2000 until PGP 6.5.2a (PGP 6.5.1 refuses to install at all on Windows 2000). Once you get to PGP 6.5.2a, you can format PGPdisk volumes as FAT16 or FAT32, but earlier versions of PGP only allow Windows 2000 to do NTFS-formatted PGPdisk volumes. Again, strange.

Note: PGPdisk from PGP 6.5.8ckt appears to provide more leeway with FAT16 and FAT32 host drives on Windows NT4 and Windows 2000, allowing the max file size (and, thus, max volume size) to go up to 4095 mb. In this respect,  the CKT builds behave more like the PGP 7.x builds from NAI -- for Windows NT 4 and Windows 2000, at least. PGP 6.5.8ckt will even let Windows NT4 and Windows 2000 users format PGPdisk volumes > 2 gb as FAT16, which even NAI's PGP 7.x won't do.

Conclusion

The two big remaining questions are:

• What is the absolute upper limit for FAT32-formatted PGPdisk volumes on NTFS host drives?
  Is that limit the same for PGP 6.0.x/6.5.x and 7.x/8.0?
   
• What is the absolute upper limit for NTFS-formatted PGPdisk volumes on NTFS host drives?
  Is that limit the same for PGP 6.0.x/6.5.x and 7.x/8.0?

Unfortunately, I don't know the answers to those questions. The final answers may not be of practical consequence anyway, since I think it debatable whether anyone could be advised to store mass amounts of sensitive data in PGPdisk container volumes of more than a few gb anyway.

Links

For information on PGP compatibility issues, see:

• PGP Compatibility Tables

For information on the compatibility of PGPdisk (and other PGP add-ons) with various versions of Windows, see:

• PGP Add-on Components

And, finally, for information on where to find various versions of PGP on the Internet, see:

• PGP Versions, Sources, & Alternatives

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© 2000, 2001, 2002 Eric L. Howes