Grounding hard disk cage?

[rthorntn]

Hi,

I basically ripped the 24x SAS/SATA drive cage and backplane out of an 7-year-old Supermicro 216BA-R920LPB case that was running 24/7 for 5 years (drilled the rivets out), the backplane (SAS216A, photo attached) has 6 long horizontal gold traces right at the bottom (below the molex connectors), the 216BA-R920LPB case has a long thin metal bar attached that touches those 6 traces, I'm going to run it "barebones" externally wondering if I need to worry about it?

Thanks!

Cheers
Richard

[Manul]

My guess is that these contacts are there for EMC reasons. So basically you do not need to worry about it, unless you have sensitive radio equipment nearby, that sort of things. Of course it is not good practice to disrespect electromagnetic emissions, but to be fair, there is so much radio pollution everywhere (from cheap consumer stuff, cell towers and who knows what else), that it almost does not matter anymore.

[fordem]

Just remember that EMI/EMC is a two way street, but, that's not my real reason for posting - if you plan on running 24 disks, you'll need to consider some sort of forced air cooling.

[rthorntn]

Dang I lost my last post.

Thanks!

I got to thinking with this backplane, will it be OK to run it from a different ATX PSU to the PSU that's powering the motherboard?

Just being paranoid.

Cheers
Richard

[fordem]

As long as the DC grounds are bonded together, which they will be through the data cables, I see no reason why there should be a problem.  Have you ever seen/used an ESATA external drive with a separate power supply?

That's the equivalent of what you're attempting.

[rthorntn]

Thanks @fordem

My thinking was the "external" SAS cables (SFF-8088, SFF-8644) tended to have metal casings on the connectors, the "internal" cables (SFF-8087, SFF-8643) have plastic casings, I'll be using SFF-8087 to SFF-8643 cables.

Now I'm thinking the metal might just be for durability.

[fordem]

I'm not talking about data cable connectors, I'm talking about the data cables themselves - google SAS or SATA pinout and look at the connections, you'll see the two pairs of differential connections, and grounded wires in between them (to reduce cross talk) - a SATA data cable has one pair of connections for transmit, a second pair for receive, and three separate ground connections.