Era target (EXPERIMENTAL)

modulename: dm-era.ko

configname: CONFIG_DM_ERA

Linux Kernel Configuration
└─>Device Drivers
└─>Multiple devices driver support (RAID and LVM)
└─>Era target (EXPERIMENTAL)
In linux kernel since version 3.15 (release Date: 2014-06-08)  
dm-era tracks which parts of a block device are written to
over time. Useful for maintaining cache coherency when using
vendor snapshots.

source code:
drivers/md/