hcp

hcp

Hot Copy creates point-in-time snapshots of any Linux block device

hcp [--mount-point] [--skip-mount] [--read-only] [-c DEVICE] [-q QUOTA] [DEVICE]

hcp -l

hcp -r [DEVICE]

hcp -s [DEVICE]

DESCRIPTION

Hot Copy creates a consistent point-in-time snapshot of a Linux block device.  Hot Copy does not use LVM.  Hot Copy snapshots are readable and writable.  Hot Copy by default uses the free space on the real block device to store changed blocks.  

COPY-ON-WRITE CHANGED BLOCKS STORAGE

A copy-on-write method is used so Hot Copy uses no space until your real block device is changed.  As writes are made to the real block device Hot Copy makes a block-level backup copy of blocks before they are overwritten.  The changed blocks are stored in the Hot Copy changed block storage device.  This can be specified with the (-c) option.  By default changed blocks are stored on the same block device you are taking a Hot Copy of.  To prevent the Hot Copy changed blocks from potentially filling up your storage device with changed blocks during the copy-on-write used to maintain the snapshot hcp uses a free space quota.   If the percentage of free space on your changed blocks storage device is less than or equal to this percentage (default is 5%) then the Hot Copy will stop working.

WRITABLE HOT COPIES

Hot Copies are both readable and writable.  When you write to the Hot Copy as your writes are made changed blocks must be stored and space is consumed on your changed blocks storage device.  If you prefer read-only snapshots you can specify your Hot Copy be mounted with read-only with the -o command line option.

DEVICE DRIVER

Hot Copy requires a Linux Device Driver, which must be installed.   The hcp-setup utility is used to build a hcp device driver for your running kernel.  See hcp\-setup.

OPTIONS

-m, --mount-point specify mount point of Hot Copy (default is /var/hotcopy/device)

--skip-mount do not mount the Hot Copy

-o, --read-only mount the Hot Copy read-only

-c, --changed-blocks specify an alternate device to store changed blocks

-l, --list list active Hot Copies

-r, --remove remove specified Hot Copy device

-q, --quota specify free space quota for change blocks storage (default is 5%).  If your changed blocks storage device has less than or equal to this percentage of free space the Hot Copy will be aborted.

-s, --show-hcp-device print the Hot Copy device (/dev/hcpX) corresponding to the real block device given

-v, --version print version information about hcp command line utility and hcp device driver

-h, --help print help dialogue

DEVICE the block device to make a snapshot of.

QUOTA integer percentage of free space quota for changed blocks.

EXAMPLES

Create a new Hot Copy session:

          hcp /dev/sdb1

Remove a Hot Copy session:

          hcp -r /dev/hcp1

List available Hot Copy sessions:
        
          hcp -l
      
Create a new Hot Copy session with a specified free space quota for changed blocks of 10%:

          hcp -q 10 /dev/sdb1

Report bugs to http://forum.r1soft.com

COPYRIGHT

Copyright 2008 - 2012 Idera, Inc. 

SEE ALSO

hcp-setup, hcp-device