Mirror

• Maintains identical copies of data on devices.

• Divides the device being copied into regions typically 512KB in size.

• Maintains a (small) log with one bit per region indicating whether or not each region is in sync.

• Two logs are available – core or disk.

• Parameters are:

  • mirror <log type> <#log parameters> [<log parameters>] <#mirrors> <device> <offset> <device> <offset> ...

• The disk log parameters are:

• <log device> <region size> [<sync>]

• <sync> can be sync or nosync to indicate whether or not an initial sync from the first device is required.