I have a Dell Precision T3610 workstation that currently has two 3.5" SATA HDDs installed, and I'd like to add two more 2.5" disks in a hot-swap bay. I have two free SATA ports, but I'm struggling to find a way to provide power for the additional drives.
The only spare power connector on the PSU is an 8-pin PCIe block designed to provide power for a second graphics card. The machine has a 685W power supply – my intuition is that if the PSU is designed to provide enough power for a second graphics card then it should probably be able to handle a couple of extra 2.5" HDDs (which would should only draw about 3-4W apiece) but I admit that I have not done all of the math to confirm this.
I've come across various SATA-to-PCIe power adaptors (e.g. this), but so far I haven't found the converse (i.e. male PCIe to female SATA). I suspect that there is a good reason for this – my understanding is that PCIe power connectors provide ground and +12V pins, whereas SATA also requires a +5V pin (and possibly +3.3V as well for old drives). Can anyone confirm whether my suspicions are correct, and it is impossible to power a SATA drive from a PCIe connector?
Another possibility I'm considering is whether I can use a couple of y-adaptors to split the power supply to my two existing 3.5" HDDs in order to provide power for the two additional drives. Does this sound like a reasonable approach to try?
Best Answer
The y-adapter is reasonable, and something you can calculate beforehand.
The HDD manufacturer should provide a product specification listing the maximum amperage draw for the rails it uses (example). A power connector supplies a total of 4.5 A for each voltage, so knowing if you have enough power is something you can check
Usually 3.5" drives use the 12V rail or both the 12V and 5V rail, and 2.5" drives just the 5V rail.
The 3.5" drives will draw more current, and some drives can draw more than 2.25 A, so it may be better to put them on different y-cables. Using the y-cable for a 3.5" and 2.5" is probably nothing to worry about at all.