Your primary HDD is a SATA 3 device, so the slot/interface on the motherboard is a SATA 3, and this can get data transfer speed up to 600 Mb/s. On the other hand the optical drive doesn't always have the same slot/interface as the HDD on the motherboard...so it could be a SATA 2 (or 1), mainly because it doesn't need that much speed for data transfer as the hdd. So, if you put a SATA 3 SSD on a SATA 2 interface you will get only up to 300 Mb/s.
And you should think about build quality on 2nd hdd caddy...sometimes the caddy itself could limits the data speed transfer.

הבעיה היחידה שהייתה לי עם המחשב שלי (dell xps m1530) שהייתי צריך לפרק לו הכל עד השלדה בשביל להוציא את ה-CD
יש מחשבים שהוצאת ה-CD זה עניין של 2 ברגים.