Linux Server Hacks, Volume Two

Hack #46. Create Flexible Storage with LVM

"User disk requirements expand to consume all available space" is a fundamental rule of system administration. Prepare for this in advance using Logical Volume Management (LVM).

When managing computer systems, a classic problem is the research project or business unit gone haywire, whose storage requirements far exceed their current allocation (and perhaps any amount of storage that's currently available on the systems they're using). Good examples of this sort of thing are simulation and image analysis projects, or my research into backing up my entire CD collection on disk. Logical volumes, which are filesystems that appear to be single physical volumes but are actually assembled from space that has been allocated on multiple physical partitions, are an elegant solution to this problem. The size of a logical volume can exceed the size of any of the physical storage devices on your system, but it cannot exceed the sum of all of their sizes.

Traditional solutions to storage management have their limitations. Imposing quotas [Hack #55] , can prevent users from hogging more than their fair share of disk resources, helping your users share their resources equitably. Similarly, paying scrupulous attention to detail in cleaning out old user accounts can maximize the amount of space available to the active users on your system. However, neither of these approaches solves the actual problem, which is the "fixed-size" aspect of disk storage. Logical ...