Although the ext2 filesystem[4] was not the first filesystem used by Linux and while other filesystems have attempted to lay claim to being the native Linux filesystem (for example, when Frank Xia attempted to rename xiafs to linuxfs), nevertheless most would consider the ext2/3 filesystem as most deserving of this distinction. Why is this? Why have so many system administrations and users put their trust in the ext2/3 filesystem?
There are many possible explanations, including the fact that the filesystem has a large and diverse developer community. However, in our opinion, robustness (even in the face of hardware-induced corruption) and backwards compatibility are among the most important reasons why the ext2/3 filesystem has a large and loyal user community. Many filesystems have the unfortunate attribute of being fragile. That is, the corruption of a single, unlucky, block can be magnified to cause a loss of far larger amounts of data than might be expected. A fundamental design principle of the ext2/3 filesystem is to avoid fragile data structures by limiting the damage that could be caused by the loss of a single critical block.
This has sometimes led to the ext2/3 filesystem's reputation of being a little boring, and perhaps not the fastest or the most scalable filesystem on the block, but which is one of the most dependable. Part of this reputation can be attributed to the extremely conservative design of the ext2 filesystem [4], which had been extended to add journaling support in 1998, but which otherwise had very few other modern filesystem features. Despite its age, ext3 is actually growing in popularity among enterprise users/vendors because of its robustness, good recoverability, and expansion characteristics. The fact that e2fsck is able to recover from very severe data corruption scenarios is also very important to ext3's success.
However, in the last few years, the ext2/3 development community has been working hard to demolish the first part of this common wisdom. The initial outline of plans to ``modernize'' the ext2/3 filesystem was documented in a 2002 Freenix Paper [15]. Three years later, it is time to revisit those plans, see what has been accomplished, what still remains to be done, and what further extensions are now under consideration by the ext 2/3 development community.
This paper is organized into the following sections. First, we describe about those features which have already been implemented and which have been integrated into the mainline kernel in Section 2. Second, we discuss those features which have been implemented, but which have not yet been integrated in mainline in Section 3 and Section 4. Next, we examine the performance improvements on ext3 filesystem during the last few years in Section 5. Finally, we will discuss some potential future work in Section 6.