Hot copy
Hot Copy (hcp) is an online disk snapshot application for Linux computers, produced by R1Soft. Hot Copy CREATES point-in-time snapshots of a disk while it is running. It is similar to the snapshot feature of Linux LVM2.
Features
Hot Copy can:
- Create online disk snapshots while a Linux computer is running.
- Take snapshots so that the computer's file system is in a consistent state.
- Use a copy-on-write snapshot method to efficiently grow snapshot storage as changes are made.
- Create writable and read-only snapshots.
- Work without dedicated snapshot storage using unused portions of the computers disk to store changed disk blocks.
Implementation
Hot Copy is implemented as Linux block device driver and is distributed as a loadable kernel module and command line utility (hcp). Hot Copy filters reads and writes to the real disk and performs a copy-on-write when changes are made to the disk. Unused areas of the hard disk are used to store changed blocks in order to maintain a point-in-time snapshot.
Compared to Logical Volume Manager Snapshots
Hot Copy has several differences when compared to Logical Volume Manager snapshots:
- In order to use LVM the computer's file system must be located on an LVM Volume Group. Many Linux computers do not use LVM. Hot Copy can work with any Linux block device.
- When LVM is used the computer's root device may not be located on LVM making it ineligible for LVM snapshots.
- LVM requires dedicated physical snapshot storage for changed blocks. This requires that the server administrator configure LVM when the system is set-up in a way that reserves special storage for LVM snapshots.
- LVM is licensed under an Open source license.
Limitations
- Hot Copy is limited to creating only one snapshot per block device at a time.
- Hot Copy does not support 2.4 Linux kernels, only 2.6 is supported.
See also
- Logical Volume Manager (Linux)
- Snapshot (computer storage)