Oct 312011

Is it possible to get excited about a technology we never notice when using a computer? File systems do their job and we never give them a second thought. On a fresh setup of Ubuntu 11.10 I have 10 different mkfs.* binaries, allowing the creation of as many file systems. Why is there more than one? Let’s take a look at one I find truly exciting: btrfs, the newest entry in the Linux file system zoo.

What is it?

Btrfs is a file system designed to handle large amounts of data. It is capable of organizing volumes of up to 16 EiB and supports a maximum file size of 16 EiB. To ensure a consistent file system state, it uses copy-on-write, meaning it writes data to new locations and then updates the entry in the file system trees, so the changes only become visible once they have been completed. As a comparison: ext4 (which is the newest update of the ext-family of file systems traditionally used on Linux) supports 1 EiB volumes (1/16) and 16 TiB file sizes (1/2^20). And ext4 is a journaling file system. It records changes to be made before making them so the system state can be restored in the event of a crash.

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