R1Soft Hot Copy is an online disk snapshot

Snapshot (computer storage)

In computer systems, a snapshot is the state of a system at a particular point in time. The term was coined as an analogy to that in photography. It can refer to an actual copy of the state of a system or to a capability provided by certain systems....

 application

Application software

Application software, also known as an application or an "app", is computer software designed to help the user to perform specific tasks. Examples include enterprise software, accounting software, office suites, graphics software and media players. Many application programs deal principally with...

 for Linux

Linux

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...

 computers, produced by R1Soft

R1Soft

R1Soft is a division of BBS Technologies an international computer software company, dealing in the area of Continuous Data Protection, disk-based online backups, disaster recovery, and bare-metal restore in both Windows and Linux servers.-History:...

. Hot Copy creates point-in-time snapshots of a disk while it is running. It is similar to the snapshot feature of Linux LVM2

Logical Volume Manager (Linux)

LVM is a logical volume manager for the Linux kernel; it manages disk drives and similar mass-storage devices, in particular large ones. The term "volume" refers to a disk drive or partition thereof...

.

Features

R1Soft Hot Copy can:

• Create online disk snapshots while a Linux computer is running.
• Take snapshots so that the computer's file system
  File system
  A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...
  
   is in a consistent state.
• Use a copy-on-write
  Copy-on-write
  Copy-on-write is an optimization strategy used in computer programming. The fundamental idea is that if multiple callers ask for resources which are initially indistinguishable, they can all be given pointers to the same resource...
  
   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.
• Can create multiple snapshot versions of each block device

Implementation

R1Soft Hot Copy is implemented as Linux block device driver

Device driver

In computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device....

 and is distributed as a loadable kernel module

Loadable Kernel Module

In computing, a loadable kernel module is an object file that contains code to extend the running kernel, or so-called base kernel, of an operating system...

 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

R1Soft Hot Copy has several differences when compared to Logical Volume Manager

Logical Volume Manager (Linux)

LVM is a logical volume manager for the Linux kernel; it manages disk drives and similar mass-storage devices, in particular large ones. The term "volume" refers to a disk drive or partition thereof...

 snapshots:

• In order to use LVM the computer's file system must be located on an LVM Volume Group
  Volume group
  Volume Group is the highest level abstraction used within the Logical Volume Manager . It gathers together a collection of Logical Volumes and Physical Volumes into one administrative unit....
  
  . Many Linux computers do not use LVM. Hot Copy can work with any Linux block device
  Device file system
  In Unix-like operating systems, a device file or special file is an interface for a device driver that appears in a file system as if it were an ordinary file. There are also special device files in MS-DOS and Microsoft Windows...
  
  .
• 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.

See also

• Logical Volume Manager (Linux)
  Logical Volume Manager (Linux)
  LVM is a logical volume manager for the Linux kernel; it manages disk drives and similar mass-storage devices, in particular large ones. The term "volume" refers to a disk drive or partition thereof...
  
  
• Snapshot (computer storage)
  Snapshot (computer storage)
  In computer systems, a snapshot is the state of a system at a particular point in time. The term was coined as an analogy to that in photography. It can refer to an actual copy of the state of a system or to a capability provided by certain systems....
  
  
• Btrfs
  Btrfs
  Btrfs is a GPL-licensed copy-on-write file system for Linux.Development began at Oracle Corporation in 2007....
  
  - A file system with similar feature

External links

• R1Soft Hot Copy
• R1Soft Hot Copy Documentation