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The creator of the Windows formatting tool reveals the reason for the 32 GB limit on FAT32 partitions: “Because I said so”

27 mayo, 2021

Dave Plummer worked as a software engineer for Microsoft in the days of Windows 95 and Windows NT 4.0. Today he has a YouTube channel where he talks about the history of the company; specifically his latest video deals with the history of Windows Format, the Microsoft program that allows you to format disks (hard and removable) and that it has changed very little since he programmed it.

But, beyond that, also take the opportunity to clarify the reason for the 32GB limit on FAT32 formatted partitions; a limit that seemed far away when it was established, but that, years later, motivated the creation of the xFAT format to allow Windows to take advantage of the growing storage capacity of hard drives and USB drives.

A totally arbitrary limit

In his video, Plummer shows the camera a microSD card and, after recounting how useful it is in drones, cameras and other devices, asks us if we know why, if we wanted to, we would be unable to use graphical drive formatting tool to format it in FAT32 using all its storage capacity.

FAT32, NTFS or exFAT: which file system to choose when formatting your hard drive or USB

“Because I say it”, answer back. “Yeah, that’s how my kids look at me when I say those things, but in this case it’s literally true.”

In fact, physically FAT32 supports much larger storage volumes, but the maximum size of its clusters is determined by the size of the bits used (32, as the name implies), such that the larger the volume, the more space is wasted.

FAT32 was released alongside Windows 95 OSR2 to overcome the limitations of FAT16. But he introduced different ones.

Thus, if you have a text file of a few bytes and you save it on a FAT32 disk with 32K clusters, instead of a ten bytes it will occupy a whole cluster (32768 bytes), which means wasting more than 99.9% of the space. “So, at what point do you say ‘No, it’s too inefficient, would it be crazy to let you do that?’

“I imagine my thought process went something like this: The memory card I was using for testing was 16MB, because it was the largest I could get … maybe I multiplied its size by a thousand, and then doubled it again to be safe, and I thought that would be more than enough for the lifespan of NT 4.0 “.

“I chose 32 gigabytes as the limit and then went on with my daily routine. I didn’t start to regret that choice until SD cards hit the magic size of 32GB many years later.. [Mi error] It has been going on for 25 years, with no one appearing to have made any substantial changes to Format since then … “.

Although Plummer is also surprised by some rumors about the ulterior motives of his decision, such as that it was “a sinister plot to promote the adoption of NTFS“.

Currently, both NTFS (the file system used by default on hard drives in Windows) as exFAT (most used on removable storage devices) ignore these arbitrarily set limits by Plummer.

Even Microsoft’s own command-line tools (let’s not talk third-party developed ones anymore) allow you to create “a disk as big and inefficient as you want”, always within the technical limits of FAT32.

Via | The Register