D390 and SCSI drives SE/DE

[nickoli]

Have some HP D390 servers configured with a RAID enclosure. The CPU has a CD/DVD ROM and one Double Ended SCSI harddrive. The RAID enclosure attaches to the CPU via a SCSI (Double Ended to tolerate longer cable length) cable. However the hard drives in the RAID enclosure are Single Ended SCSI drives.

I thought I read somewhere that the built-in SCSI controller will work either double ended or single ended. I suspect that the CD/DVD device is single ended, but the drive "cage" and the external connection are double ended to support the RAID box.

We don't need the RAID for our current application. I tried using one of the RAID (SE) drives along with the internal (DE) drive, but it was un-recognized by the system. If I remove the Double Ended SCSI drive, and plug in Single Ended drives, will the controller "switch" over to the single ended
mode? Or are there other things done to the SCSI system? (I am trying to expand the filesystem capability of the D390, and if I can "steal" two SE drives from the RAID enclosure I would be happy. Even though this means giving up
the lone double ended SCSI drive and the capability to connect to the RAID box I currently have.)

I am making the assumption that a "normal" D390 without the RAID box would use Single Ended SCSI drives.

 

[Guest_imported]

What is the make and model of your RAID array? You didn't specify if it was an HP or not...

I'm not sure what you mean by "double-ended". If you mean "Fast, Wide, Differential" (FWD) which was popular on HP systems of that vintage, then no ... you can't mix single-ended and FWD drives at all. If your array needs FWD, then you will need to install a FWD SCSI adapter in the D390.

Now, you CAN mix single-ended and "LVD" (Low-voltage differential) SCSI, which is the current high-performance SCSI out there, but the D-class doesn't have LVD capabilities and I don't know if there is an LVD interface available for it. If your array needs LVD, not FWD, then yes you could plug it into the same SE SCSI chain your CD is on, but you would only be running it at SE speeds (5 MB/sec peak) so you would really be crippling your performance.