Hello,

I need two responses of at least 150 words each for the below students discussions for this week. Also in the bold below are the questions the students at answering.

1) Using course resources and the Internet, please explain the following Linux Filesystems:

a.  ext1 (Extended File System)
b.  ext2 (Second Extended File System)
c.  ext3 (Third Extended File System)

Student one:

1) Using course resources and the Internet, please explain the following Linux Filesystems:

a.  ext1 (Extended File System)

b.  ext2 (Second Extended File System)

c.  ext3 (Third Extended File System)

           The ext1, or otherwise known as plain old ext from what I’ve read, was a file system developed by a guy named Remy Card in the early 90’s.  Going back a little further, it seems that when Linus Torvalds developed the first Linux kernel in ‘91, at its inception, it was really depending on the same file system that MINIX utilized. (Salter, 2018)  This wasn’t all that great, because it could only handle file names up to 14 characters, and address only a mere 64 MB of storage.  At that time in history, the typical hard drive was already anywhere from 40 – 140 MB.. obviously.. this was an issue, and thus, ext came to be.  In ’92, ext was introduced as a way to alleviate some of the most frustrating parts of using MINIX, i.e. ext could handle up to 255-character file names and address up to 2 GB of data. (Salter, 2018)  A big improvement, obviously.  One point to note is that ext was not necessarily meant for commercial application.. it was more of a pet-project, or as Salter put it, a “toy”.

           Just a short year after the release of ext, the same guy, Remy, developed and released ext2.  This new system was released not so much as a “toy”, but as a commercial-grade file system ready for the big leagues right out of the box.  This new system utilized the same metadata structures as the old ext file system, however, it allowed for more disk space to be left between the metadata structures for future use. (Both, 2017)  In the end, the ext2 file system was a big improvement over ext, so much so that it really snuffed ext out rather quickly.  With that said, though, there were still a couple drawbacks of the ext2 filesystem.  In the event of a crash, the file system check (fsck) took an extremely long time to locate and correct issues in the filesystem. (Both, 2017) In addition, there was also issue with significant performance loss due to fragmentation (the storage of a single file in multiple places, scattered around a rotating disk). (Salter, 2018)  So, ext2, because of the specific way it works, i.e. low amount of actual disk writing, makes it useful in things such as USB flash drives.. although, items such as exFAT and FAT32 do the same thing, and are more widely compatible.. so, although you may still see ext2 today, it’s likely used for a specific reason. (Garrison, 2017)

           Lastly, ext3 showed its face around 1998.  This filesystem was the result of improvements made to ext2, done so by a guy named Steven Tweedie. (Salter, 2018)  So, likely the most significant addition to the filesystem at this point would be the inclusion of a process called journaling.  Where earlier versions were susceptible to corruption due to something such as a sudden power loss, ext3 implemented journaling, which is a “special allocation on disk, where writes are stored in transactions.” (Salter, 2018) The idea seems to be that this specially allocated area can act as a neutral ground for writes.  If the write is able to finish, it gets committed to the filesystem.  If the write is interrupted, it basically means the file being written is lost, but it leaves the rest of the system alone and intact.. which is a good thing.

Nick

Both, D. (2017). An introduction to Linux’s EXT4 filesystem. Retrieved from https://opensource.com/article/17/5/introduction-ext4-filesystem

Garrison, J. (2017). Which Linux File System Should You Use? Retrieved from https://www.howtogeek.com/howto/33552/htg-explains…

Salter, J. (2018). Understanding Linux filesystems: Ext4 and beyond. Retrieved from https://opensource.com/article/18/4/ext4-filesyste…

Student two:

   This week we dive into Linux file systems and the various forms of ext files. Looking into filesystems and the meaning behind it has led me to two different meanings. They are both commonly used and can be confusing to novices. The first meaning the entire hierarchy of directories also known as the directory tree. It is used to organize files on a computer system. Both the Linux and Unix start with a root directory that leads to a series of subdirectories which also contain more subdirectories. The second meaning is the type of filesystems that organize stored data on a computer disk or partition. Each filesystem has its own rules for controlling the allocation and the associating data about each file. Certain info can also be found like the file name, the location of the file, permissions, and creation date (Linfo, 2004). 

   Diving into the various forms of EXT files we come across three and they are ext1, ext2, and ext3. The first file is ext1. Ext1 (Extended File Systems) was first released in April of 1992 and is an extension of the Minix file system. The total amount of partition size is 2 GB and comes with a maximum file name size of 255 characters. Its major limitation is the inability to support separate access, node modification, and data modification. The ext2 file was later introduced the following year in January by Remy Card. The significant improvements made by the ext2 was sophisticated algorithms that improved speed and maintained additional time stamps. Its only drawback is its inability to support journaling features (Natarajan, 2011). The superblock that keeps track of the status of each file identifies whether or not it is clean or dirty by automatically scanning itself (Arnes, 2018). The maximum file size can be anywhere between 16 GB to 2 TB, while overall system sizes can be between 2 to 32TB. The last ext file is the third extended file system which was introduced in 2001 by Stephen Tweedie. This version of ext is a journaling version of ext2 and is used with Linux operating systems. The ext3 can also be mounted and utilized as an ext2 and utilize all of the utilities within ext2. Some of the improved mechanics behind the ext3 are tracking modifications or changes. If a system were to crash, the possibility of data corruption is slim (Natarajan, 2011). Within the journaling, there are three versions which are a journal, ordered, and write back. Each plays an intricate role within the program. For example, journaling saves content and metadata, ordered allows the user to only save metadata only after writing the content, and writeback saves metadata like the ordered but this can happen before or after the content is written.

References

Årnes, André. ( © 2018). Digital forensics. [Books24x7 version ]

Linfo. (2004, April 16). Filesystems: A Brief Introduction. Retrieved July 9, 2019, from http://www.linfo.org/filesystem.html

Natarajan, R. (2011, May 19). Linux File Systems: Ext2 vs Ext3 vs Ext4. Retrieved July 10, 2019, from https://www.thegeekstuff.com/2011/05/ext2-ext3-ext…

-Cesar