Understanding Linux Ext Filesystems, RAID, and LVM
This article explains the structure of Linux Ext (2/3/4) filesystems, detailing superblocks, inode tables and data blocks, then describes block groups, the role of superblocks, and outlines the differences between hardware and software RAID as well as the principles and risks of using LVM for flexible storage management.
The Linux Ext (2/3/4) file system is composed of a Super Block, an inode table, and data blocks. These components store metadata and the actual file data.
Because storing all inodes and blocks together would be inefficient, Ext formats the disk into multiple block groups, each containing its own inode table, data blocks, and a copy of the superblock, similar to how a military division is divided into brigades.
The Super Block records essential filesystem information, including total numbers of blocks and inodes, counts of used and free inodes/blocks, block and inode sizes, timestamps for mounting, last write, and last fsck, as well as a valid‑bit indicating whether the filesystem is currently mounted.
RAID implementations are divided into hardware RAID, which uses a dedicated RAID controller card offering high performance without consuming CPU or memory, and software RAID, which relies on the operating system (e.g., the mdadm tool on Linux) and consumes CPU and I/O resources; hardware RAID appears as /dev/sdX devices, while software RAID appears as /dev/mdX devices.
Logical Volume Manager (LVM) provides flexible resizing of filesystem capacity by aggregating multiple physical partitions or disks into a volume group (VG), creating logical volumes (LV) that can be resized as needed, though it does not improve performance or data safety and can lead to data loss if the LVM fails.
The article includes download links for "Linux LVM Logical Volume Management Technology" and "Linux Filesystem, Software RAID, and LVM Introduction" as well as references to several market research reports such as the China PaaS Market Report (2021), China SaaS Market Report (2021), and various cloud computing whitepapers.
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