從表面上看，作業系統的檔案系統可能看起來像一大堆資料夾，但肯定還有更多的資料夾。請繼續閱讀，我們將調查檔案系統表面下的內容。

今天的問答環節是由SuperUser提供的，SuperUser是Stack Exchange的一個分支，是一個由社群驅動的問答網站分組。

問題

超級使用者讀者P\u Q對檔案系統很好奇，他寫道：

I have used Windows since childhood, and when I hear the phrase “Windows files system” I think of directories (folders) within directories, a folder called SYSTEM, a folder called PROGRAM FILES, etc. Is this what the system is? Just the layout of the folders?

And then I recently started using Linux, and my reference book says in the Linux filesystem everything starts at root and branches off from there. How is that really different from Windows? I mean, it seems the Linux system and the Windows system are just two ways of setting up a directory tree. Is this what file system means?

這種簡單的檔案系統描述方式是最準確的嗎？讓我們再深入一點。

答案

超級使用者貢獻者tomwij**an對Windows和Linux作業系統中的檔案系統結構進行了深入的研究。他寫道：

Just the layout of the folders?

Sounds too good to be true…

Let’s take the FAT32 file system as an example. I can install Windows XP on it, but I can also use it on a memory card. On a memory card, you don’t have those folders that you sum up.

So… Don’t confuse the directory layout of a family of operating systems with a file system.

Is this what a file system means?

No… It refers to the underlying bits and bytes that make your directory structure work.

The underlying bits and bytes? Show me FAT32!

Let’s look at what FAT32 looks like, it has:

• Some header sectors in the beginning, like Volume ID and Reserved Sectors
• Two File Allocation Tables, allowing us to figure out where our files are.
• Clusters containing all our directory and file data.
• Some very **all unused space that we can’t use.

A FAT table c***ists of a lot of entries that look like this, allowing us to determine where the directory or file is stored in the clusters space, as well as some attributes and size.

A directory entry would point to a list of directory/file entries…

In the clusters space, we can now travel our clusters to find the data we need. A cluster essentially contains data and information where the next fragments are

Do other file systems differ? Show me NTFS!

I’m going to show you an image so you can notice the differences, the rest is homework for the reader: More information can be found on this blog archive or Google.

The main idea is that NTFS is a huge improvement over FAT32 that is more robust/efficient. Having a better idea of (un)used space by using a bitmap to further help against fragmentation. And so on…

What about the file systems on Linux? Show me ext2/3!

The idea is that ext2/ext3 use super blocks and inodes; this allows for soft and hardlinks, directories that are files, files with multiple names and so on. The main gist is abstracting away to allow the file system to be capable of doing more meta-ish stuff…

有關檔案系統的更多閱讀，請參閱以下How to Geek文章：

• HTG解釋：Linux目錄結構解釋
• HTG解釋說：您應該選擇哪個Linux檔案系統？
• 我的USB驅動器應該使用什麼檔案系統？

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