If unsure, say N.
+config MD_AUTODETECT
+ bool "Autodetect RAID arrays during kernel boot"
+ depends on BLK_DEV_MD=y
+ default y
+ ---help---
+ If you say Y here, then the kernel will try to autodetect raid
+ arrays as part of its boot process.
+
+ If you don't use raid and say Y, this autodetection can cause
+ a several-second delay in the boot time due to various
+ synchronisation steps that are part of this step.
+
+ If unsure, say Y.
+
config MD_LINEAR
tristate "Linear (append) mode"
depends on BLK_DEV_MD