Computer file systems

Choosing the right file system for your computer can have a large impact on how well your computer works. I won’t claim I know everything about file systems, but I will share what I know, which should be enough to give you a basic idea of how these things work.

According to Wikipedia, a file system is “a method for storing and organizing computer files and the data they contain to make it easy to find and access them.” Most people don’t think too much about the file system, if they think about it at all.

Before I discuss the different file systems, here’s a brief technology lesson. Sectors are the smallest usable space on a drive. A sector is a fixed-length “memory block” whose size depends on the file system used and the size of the drive. For better system management, sectors can be combined into clusters. A cluster is the smallest logical amount of disk space that can be allocated to hold a file. The cluster size is important when it comes to file size because even if an entire cluster isn’t filled, it’s still considered used. Put another way, if a file is 4 KB and the sector size is 512 bytes, 7.8 clusters are needed to hold the file. Therefore 7 complete clusters and 0.8 of another are required to hold the file. However, even though the 0.8 doesn’t fill a complete clusters, that clusters is considered used. No additional information can be added to that clusters. Obviously if your clusters sizes are large, more drive space is lost to this clusters allocation. Hence one of the reasons file systems are continually improved.

Rather than give you a boring history of file systems, I’ll just touch on the main ones you’ll run into and how they compare. To start in the Microsoft Windows world, the two main file systems are FAT and NTFS.

Windows File Systems

FAT, which stands for “File Allocation Table”, has had several incarnations with the most common ones nowadays being FAT16 and FAT32. FAT16 is usually only found on memory cards and other small devices because it has a maximum memory size of 2 GB. FAT16 is also not very file-friendly because it doesn’t scale well as file size or disk size increases; the cluster sizes get so big that you lose a large percentage of your space to partial clusters. There was also a length limit on file names; a file name could only have a maximum of 8 main characters and a 3 character extension.

FAT32 improved on this by increasing the maximum hard drive size to 128 GB. It also introduced the idea of long filenames greater than the original 8.3 limit. (This idea had been introduced earlier under VFAT but now it was fully a part of the file system).

One of the problems with FAT is that is limits the size of a single file; FAT32 has a limit of 4 GB. For video editing this is often too small. Another large problem is fragmentation. Data is written sequentially on the drive. As files are deleted, free space is opened up at various places. New data is written to these free areas first, then to the rest of the disk. This causes the files to fragment as bits and pieces of them are randomly written throughout the drive. This can slow down data access which is why it’s necessary to periodically run a defragmentation tool on your hard drive.

To overcome these and other limitations, NTFS was developed for the NT line of Windows operating systems, first appearing in Windows NT 3.1. For all the nitty-gritty about NTFS, check out Wikipedia’s article. Briefly however, NTFS has many of the features of FAT32 (like long file names) with improved stability and less defragmentation. It also supports encryption without third party tools, journaling, and other features that help in a business environment. It also supports hard drive volumes up to 16 EB (10^18 bytes).

Since Windows XP and Vista are based on the NT code base, they both use NTFS as the native file systems; but if you really want you can format new hard drives as FAT if you want. (This is particularly good if you want to move an external hard drive to computers using different operating systems, since pretty much all of them understand FAT16 and FAT32 with no problems.)

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4 Responses to Computer file systems

  1. J de Silva says:

    You’re right, I never thought about the file system before today, and I would never have searched for this information myself. The one thing that stuck with me is the point about cluster and file sizes, and the potential to “lose” drive space. That’s something new I learnt today, thank you. 🙂

  2. LocalTech says:

    Hmmm… But mind you – Windows Vista is the next generation and sooner or later, Windows XP will become like Windows 98 – Extinct. So if you plan on upgrading to Windows Vista you have to have NTFS. Even when you’re trying to upgrade to Vista, it wont allow you to if you have a FAT32 File System… *sigh*

  3. I’m not denying NTFS isn’t better than FAT; it most definitely is. However, FAT is essentially universally recognized among operating systems. So if you have an external hard drive, you’re safest bet is to format it as a FAT version so you can guarantee that you’ll be able to use it on any computer.

  4. Pingback: Windows Vista File System – NTFS ONLY! | Fix My Computer!

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