Always try to use the SATA ports connected to the Intel Z68 Express Chipset first since they offer the best compatibility and performance. Those would be the two white (SATA3_0 and SATA3_1) and four blue SATA ports (SATA2_2, SATA2_3, SATA2_4, SATA2_5).
If both the Crucial SSD and Samsung 1TB HDD are SATA3 6 Gb/s devices then use the 2 SATA 6 Gb/s cables that were included in the motherboard package to connect the Crucial SSD to SATA3_0 and the Samsung 1TB HDD to SATA3_1.
The SATA DVD optical drive should be connected to SATA2_2.
The two black SATA ports, GSATA3_6 and GSATA3_7, are connected to the Marvell 88SE9172 controller and are known to be slower than the ports connected to the Intel Z68's SATA3 controller. If you don't use the Marvell SATA controller you should disable it in the BIOS setup.
I want to thank you ko888 as well. I have the same mobo and M4 setup. I was having trouble getting my firmware to update on the M4. During post, my drives weren't even showing up. I found this post and swapped the ports. Firmware updated like a charm
Well, it turns out that you cannot updgrade your firmware at all with the drive plugged into the Marvel controller, at least I was unable to, even with a boot disk.
I want to show you what a difference it made in the performance of my drive: