File system is a system to store and access the files (and directories) on any computer. Usually users don’t have to worry about which file system they are using, operating systems take care of it all. Though knowing their strength and weaknesses can sometimes help one to choose better option depending on the scenario.
There are many file systems present, suitable for different needs and can be categorized in many different categories, though we aren’t going to discuss them all here (if you are interested, you can check the list of all file system). In most Linux distributions, there is option to choose from two to five different file systems, which can be classified in two general categories:
- Journaled (or journaling) File System
- Non-journaled File System
Journaling File System:
Journaling file systems makes a log (or journal) of all the changes made before they are written to disk. This is helpful when system crash or power failure may cause loss of some data, while the changes are still being written to disk. In such case, system compares the disk state with journal, and update the disk where required, resulting in data recovery.
Every file has two parts, data and meta data. Data (or user data) is everything present in the file, that is, in case of text file it will be all the text present in file, for music file, it will be the music etc. whereas, meta data is data about data, like when was file last accessed, modified or created. Title of the song and artist information for music file and author information stored by some office programs is also meta-data.
This brings us to a sub-category of journaled file system.
- Meta-data Journaling
As the name implies, meta data journaling file systems only log the meta data of the file and not the user data. It provides better performance then complete journaling file system, but doesn’t provide full data recovery options.
Non-journaled File System:
Non-journaled file system are those which doesn’t provide journaling. Which means in case of system crash or power failure, there are chances of data getting corrupt. It also means data is written just once (as it doesn’t have to written to the journal) there are fewer read/write operations on disk compared to journaled file system, which makes it preferable to use on flash drives and other solid-state drives, which can increase their life span.
That’s all for now, in next post I will provide comparison of different file systems for linux.
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