Big Picture of the LVM

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Advantages:
- Filesystems can span disks, so size is not limited by capacity of
physical disks.
- Can expand filesystems on the fly.
- Can add additional disks to existing pool of disk space (VG).
- Can mirror important data on multiple physical disks for redundancy.
- Can "export" an entire VG so that all disks in the VG can be easily
physically disconnected, moved to another machine, and "imported".
Limitations:
- Must reducevg when removing disk.
- When a single disk in a VG dies, the whole VG is affected.
- "Brick Wall" between VGs - LVs can't cross VG boundary.
- Cannot shrink filesystems.
General Approach:
- Configuring for performance or flexibility vs. reliability or fault-tolerance.
- Strategy: Define adequate but not huge filesystems, leaving pool of free storage for later assignment.
- Seperate out data categorically onto different VGs, so that an OS upgrade will not touch user data, or so that user data can be easily moved to another machine.
Mark D. Roth <roth@feep.net>