Linux Server Hacks, Volume Two

Hack #47. Combine LVM and Software RAID

Combining the flexibility of LVM with the redundancy of RAID is the right thing for critical file servers.

RAID (Redundant Array of Inexpensive Disks or Redundant Array of Independent Disks, depending on who you ask) is a hardware and/or software mechanism used to improve the performance and maintainability of large amounts of disk storage through some extremely clever mechanisms. As the name suggests, RAID makes a large number of smaller disks (referred to as a RAID array) appear to be one or more large disks as far as the operating system is concerned. RAID was also designed to provide both performance and protection against the failure of any single disk in your system, which it does by providing its own internal volume management interface.

RAID is provided by specialized disk controller hardware, by system-level software, or by some combination of both. The support for software RAID under Linux is known as the multiple device (md) interface. Hardware RAID has performance advantages over software RAID, but it can be a problem in enterprise environments because hardware RAID implementations are almost always specific to the hardware controller you are using. While most newer hardware RAID controllers from a given manufacturer are compatible with their previous offerings, there's never any real guarantee of this, and product lines do occasionally change. I prefer to use the software RAID support provided by Linux, for a number of reasons: ...