I/O delaying target

modulename: dm-delay.ko

configname: CONFIG_DM_DELAY

Linux Kernel Configuration
└─>Device Drivers
└─>Multiple devices driver support (RAID and LVM)
└─>I/O delaying target
In linux kernel since version 2.6.24 (release Date: 2008-01-24)  
A target that delays reads and/or writes and can send
them to different devices. Useful for testing.

If unsure, say N.

source code:
drivers/md/dm-delay.c