Understanding Linux Ext Filesystems, RAID, and LVM

In Linux, the mainstream Ext (2/3/4) file systems consist of a super block, an inode table, and data blocks.

Because storing all inodes and blocks together would be unwieldy, Ext file systems are divided into multiple block groups, each containing its own inode, block, and superblock, similar to how a division is composed of several brigades.

The super block records essential file‑system information, including:

Total number of blocks and inodes.

Counts of used and free inodes/blocks.

Block and inode sizes (e.g., block 1 KB, 2 KB, 4 KB; inode 128 bytes).

Mount time, last write time, last fsck time, and other timestamps.

A valid‑bit flag indicating whether the file system is currently mounted.

RAID can be implemented as hardware RAID, using a dedicated RAID controller card that offers high performance without consuming CPU or memory, or as software RAID, where the operating system performs the calculations (e.g., using the mdadm tool), which consumes more CPU and I/O resources but is cheaper and easier to set up.

In Linux, hardware RAID devices appear as /dev/sdX , while software RAID devices appear as /dev/mdX .

LVM (Logical Volume Manager) provides flexible storage management by allowing dynamic resizing of logical volumes. It aggregates physical partitions or disks into a volume group (VG), then creates logical volumes (LV) within that group, which can be mounted like regular partitions; however, LVM does not improve performance or data safety, and a failure in LVM can lead to permanent data loss.

Download links for further reading on Linux LVM and file‑system, RAID, and LVM introductions are provided in the original article.