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I'm running VirtualBox 5.2.32 with a Windows XP virtual machine. Everything works fine. However, when I installed 6.0.10, it reports "Disk is full" when a program tries to write to a file on a FAT16 (yes, FAT16) shared partition. This only happens if I install the 6.0.10 guest additions. If I stay with the 5.2.32 guest additions, it doesn't occur. (I don't know if it would occur with a FAT32 or NTFS partition, because the program only works with FAT16, which is why I have a FAT16 partition).

From what little I remember of those times (mid-1980s), the maximum size of a FAT16 partition was 32Mb (that's Mb, not Gb) Whatever size is your FAT16 shared drive is, only the first 32 Mb will probably be recognised, unless you create multiple partitions.

You're talking about an era when a 40Mb Hard Disk was considered to be overkill (unaffordable and unusable), and most PCs (PC Clones) that had Hard Drive's were limited to 5Mb, 10Mb, or 20Mb and floppy drives of 180/360Kb. 40mb was out of reach for all but the richest!

The maximum size of a FAT16 partition with the standard hard disk sector size of 512 bytes is is 2 GB, and you can't create one that is larger (at least with a standard sector size). (The maximum cluster size is 32 KB (that's KB, not Mb). Furthermore Mb and Gb = megabits and gigabits respectively. A lower case "b" refers to bits (and is primarily used in describing network speeds). An upper case "B" refers to bytes (8-bits)).

The original PC, released in October 1981, only had two floppy drives. The XT, released in early 1983, had a 20MB Seagate hard drive. Larger drives were available for less than $100, although they required third-party partitioning software to use more than 32MB. That was a FAT12, not FAT16 limitation. With the AT, MS-DOS supported FAT16 and partitions as large as 2GB (4GB with 1024 byte sectors).

But the maximum size is irrelevant. My single FAT16 partition is 1GB, and that is more than sufficient for the program in question to run. It's not running out of space. Something in the 6.0.10 guest additions are inaccurately returning that error status to the program. If it were running out of space, it would run out of space with the 5.2.32 guest additions as well.

cdg wrote:Something in the 6.0.10 guest additions

See https://www.virtualbox.org/ticket/18766 and viewtopic.php?f=2&t=93359 it might be related...

Other than the source of both problems being the release 6.0.10 guest additions, I don't see the relationship. I'm not experiencing crashes or BSOD's --- just a "disk is full" status-code being returned from a simple disk sector write. Of course, if my program were written by Microsoft, it might just crash rather than reporting the error status.