The HPE DL380 Gen10, like any HPE server, can be purchased in multiple configurations, as seen here:
Because of this, you may unbox your server and find that not everything works “right out of the box”. In the case of our server project, we bought a DL380 Gen 10 that was going to be used as a replication target for Virtual Machine backups. We want to use all three “boxes” of hard drive slots. Pretty simple: just a server full of large form factor SAS drives.
The server came with cables from the SAS ports on the motherboard to all three “backplanes” of the drive boxes, but only the first two boxes recognized that they had drives in them.
Turns out that first of all we had a bad SAS cable on box three, but that wasn’t the only problem. According to HPE support the third box doesn’t work unless you use a separate cable that wasn’t included.
This does make sense considering all of the possible configurations for the server. Presumable the third SAS cable that was installed would work for another common layout. Not ours, though. We needed another cable. Fortunately new servers come with next day support so we were able to get another cable the next day. (Well, the “next day” after two days of arguing with HPE support.)
If you find yourself in this situation, you need the black cable in this picture:
It is included in this kit: https://partsurfer.hpe.com/Search.aspx?SearchText=826709-B21. It is the black one with the three different types of connectors on one end and one single SAS on the other.
FYI there is also a version of the black cable that has a 90 degree, L-shaped SAS connector on the backplane end. That one will not fit for our purpose. You need the one with the straight SAS end.
To open the server so you can get to the cables, first open the latch on the top of the server and remove the cover:
The SAS cables are here:
This is how the server came out of the box, three blue SAS cables. Here is the end where they plug into the motherboard:
This is the other end, where they meet the backplane:
We need to remove the blue cable from port 3 and replace it with the black one with the three connectors on one end. You can see in this next picture where they all go.
Once you do this, all three boxes of hard drives should work.