dm-delay — The Linux Kernel 5.18.5-gnu-1 documentation

# dm-delay

Device-Mapper’s “delay” target delays reads and/or writes and maps them to different devices.

Parameters:

    <device> <offset> <delay> [<write_device> <write_offset> <write_delay>
                               [<flush_device> <flush_offset> <flush_delay>]]

With separate write parameters, the first set is only used for reads. Offsets are specified in sectors. Delays are specified in milliseconds.

## Example scripts

    #!/bin/sh
    # Create device delaying rw operation for 500ms
    echo "0 `blockdev --getsz $1` delay $1 0 500" | dmsetup create delayed

    #!/bin/sh
    # Create device delaying only write operation for 500ms and
    # splitting reads and writes to different devices $1 $2
    echo "0 `blockdev --getsz $1` delay $1 0 0 $2 0 500" | dmsetup create delayed