Powering SAS drives

[colinb]

This is an unbelievably basic question, but my Google-Fu is letting me down.

With these connectors on SAS3 drives (going back to an SFF-8643 and HBA), do I need to also/separately connect power? If yes, how?

 

[kryten]

sata power connector

 

[Sean Ho]

Those breakout cables are if you're connecting directly to the drives, without a backplane. The drives will need both data (provided by the 8643 and those blue wires) and power (15-pin SATA power to the back of those 8482 connectors). If you use a Molex-to-SATA splitter cable, you won't have to worry about PWDIS issues. If you use a SATA-to-SATA power splitter, you'll want to remove/cut the 3.3v line. Another option is to use Kapton tape to cover the third pin on the drives.

 

[sko]

"molex to sata, loose all your data"

I'd strongly recommend using a proper backplane instead of fiddling around with multiple connectors per drive. this is bound to cause problems at some time and a master recipe for data loss.

 

[colinb]

Thanks all. Connecting the SATA power cables worked. No issues with PWDIS, seemingly - all spin up.

 

[Sean Ho]

I agree that backplanes are easier to use and more foolproof. However the adage, "Molex to SATA, lose all your data" is incorrect; it came about due to the fire risk from poorly-made molded SATA power connectors that would make improper contact inside the sealed connector. Perhaps we could instead say, "Molded SATA, lose all your data".

Molex LP4 4-pin connector has been around for decades and is just fine (not as high ampacity as newer fittings, but plenty to power drives). All SM backplanes are Molex-powered.

Crimped SATA power connectors or IDC are just fine. The IDC cables are also quite easy to adjust spacing on -- pop the wires out individually by hand, and pop them back in using a flathead screwdriver (or proper tool if you like). Easy to pull the 3.3v line for PWDIS.