NTFS AND FAT file systems

Scot’s Newsletter

Information About Windows and Broadband You Can Use!

January 17, 2002 - Vol. 2, Issue No. 19

By Scot Finnie


Lowdown on the NTFS File System
A lot of you out there are budding operating system experts, whether you know it or not. If you find yourself posing questions about file systems — trust me — you're a hopeless geek. I had to own up to this exact point over a decade ago. It's painful, but it passes.
Why do I say this? Because I'm getting a steady stream of email asking for explanations about the differences between Windows XP's NTFS file system (NTFS stands for New Technology File System, and yes, NT, like Windows NT) and FAT32 (File Allocation Table), which originated in the Windows 95B version but was made popular by Windows 98, Second Edition, and ME.
Most of the questions I've been getting are from people who are considering Windows XP in one fashion or another. To make sure of my answers, I interviewed Microsoft's David Golds, group product manager for file systems and storage. And I have some useful information to pass along to you. Even if file systems sound ... yawn ... boring as heck to you, strap in and check this out for a few minutes.
If you've bought or are buying a new PC with Windows XP, the odds are extremely high that it will come with a single NTFS partition, or volume. One giant Drive C:, that is. Microsoft has tested NTFS with a single partition of up to 19 Terabytes (TB), but the theoretical maximum is at least 8 Petabytes (PB).
By contrast, FAT32 is effectively limited to volume sizes of 2TB (although this point is debatable, and this is a theoretical maximum). One of the big differences is that FAT32 doesn't scale as well as NTFS. The larger the volume size in FAT32, the larger the cluster size. At 64GB, FAT32 moves up to 16K clusters. Even a 512byte file uses 16K of space just to exist under FAT32 on a 64GB volume. That means FAT32 does not store data efficiently on larger volumes. NTFS is able to keep to its 4K cluster size default even on huge disk volumes. NTFS also stores files that are under 700bytes in the Master File Table, where they displace 1K instead of 4K, further improving storage efficiency. No other Windows file system stores files as efficiently as NTFS, especially on large disk volumes.
What's So Good About NTFS? —
It sounds like NTFS might be a hassle, so why would you want it? Surprisingly, there's just no question that you do. NTFS offers a ton of advantages. It's more secure, more efficient, just as fast as FAT32 on typical drives when properly installed, and is extensible in several ways that could make it even more useful in the future. Here's a few of the advantages:
Reliability. None of those reasons I mentioned in the previous paragraph are the main reason why I like NTFS better. What I really prefer about NTFS is that it's a journaling file system. NTFS literally keeps a log file (Microsoft calls it a write-ahead log because it writes what it's going to do before it does it) of all changes made to the hard disk. That way, if the power goes out or the operating system freezes or some other calamity occurs in the midst of a write to the disk, NTFS can resume the operation automatically as soon as the operating system is running properly again. Under the FAT file systems, that kind of situation winds up in file system or disk corruption — a sort of permanent error that can bring down the operating system or your data like a house of cards. Journaling is the main reason to use NTFS. It doesn't matter whether you're a business user or a home user, NTFS is more reliable. And reliability is what you want from your file system.
Storage efficiency. I've explained this already, so I'll keep it brief. Windows XP's NTFS is far more efficient at storing files than FAT32. In other words, you'll use less space on the disk storing a given set of 1,000 typical files under NTFS than you will with FAT32. And the larger your hard disk, the more true that is. No Windows file system is stores data more efficiently (in the least amount of disk space) than NTFS.
Drive performance. This is less black and white. Microsoft claims performance improvements on boot times. And NTFS is faster than or equal to FAT32 on smaller drives (sub 10GB) according to PowerQuest's Eggett. Microsoft has worked to maximize NTFS's performance, though; and it does appear to be inherently faster than FAT32. But as you grow into larger disk sizes, NTFS retains its smaller cluster sizes (the very attribute that delivers excellent storage efficiency). Smaller cluster sizes drag down performance. My estimate: On drive sizes over 30GB, you can expect modest reductions in NTFS performance over FAT32. According to Eggett, any such reductions really aren't noticeable. The difference is minor. That may sound pretty bad, but it's actually a pretty neat technical achievement. The performance/efficiency thing has long been a trade-off on the desktop.
One other performance point, the actual code size for NTFS is larger than for FAT32. So in a highly memory constrained environment, such as a handheld device or embedded situation, NTFS requires more space, and that can slow things down. On the typical user PC with at least 128MB of RAM, this is pretty much a non-issue.
Security. Every file in NTFS has an ACL (Access Control List). That means that technically you can create user-based security for every file on your computer. What's more, Windows XP Pro has built-in file encryption. Encryption is even preserved in backups. NTFS is far more secure than FAT32.
Disk compression. Remember how you used to use file compression before FAT32? NTFS has always supported file compression. It's just another added benefit.
Link tracking. You know how under Win98 if you create a desktop shortcut for something, if you move that target file, the shortcut is broken? Not so under XP with NTFS, which can dynamically update file shortcuts by automatically searching for the new location of the target file.
Extensibility. I could use up a lot of white space explaining NTFS's architecture. Suffice it to say that every structure in NTFS is nothing more than a simple file. The Master File Table (MFT), directories, free space map, each of these items is a file, not some special structure. Because everything is so simple, and because Microsoft designed NTFS with database properties, the file system is highly extensible, and new functions like Link Tracking, can be added easily. And there are others functions like that already. Built-in disk quotas, for example. This extensibility means that Microsoft can keep innovating with NTFS to make it more and more useful as time goes by.