having FakeRAID hardware, why is my boot slow and I see messages 'Failed to stat() /dev/mapper/"isw"'

Issue

On my system, the following boot messages are observed

failed to stat() /dev/mapper//dev/sdb:
failed to stat() /dev/mapper/"isw"
failed to stat() /dev/mapper/and
failed to stat() /dev/mapper/"ddf1"
failed to stat() /dev/mapper/formats
failed to stat() /dev/mapper/discovered
failed to stat() /dev/mapper/(using
failed to stat() /dev/mapper/ddf1)!
failed to stat() /dev/mapper//dev/sdc:
failed to stat() /dev/mapper/"isw"
failed to stat() /dev/mapper/and
failed to stat() /dev/mapper/"ddf1"
failed to stat() /dev/mapper/formats
failed to stat() /dev/mapper/discovered
failed to stat() /dev/mapper/(using
failed to stat() /dev/mapper/ddf1)!

Every message is displayed for a few seconds, causing a substantial boot delay.