sometimes things take a bit longer, like create a raid6 system over 16 harddrives 1TB with software raid...

Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md2 : active raid6 sdp[12](S) sdo[13](S) sdn[11] sdm[10] sdl[9] sdk[8] sdj[7] sdi[6] sdh[5] sdg[4] sdf[3] sde[2] sdd[1] sdc[0]
9765518720 blocks level 6, 16k chunk, algorithm 2 [12/12] [UUUUUUUUUUUU]
[>....................] resync = 0.1% (1393856/976551872) finish=25232.3min speed=643K/sec

25k minutes? I really hope the estimate is a bit off. Cause I'm not going to wait for 17 days after each test of the raid system...