I have recently acquired a new Hitachi 36G SCSI drive that is identified on bootup as:

Hitachi HUS15733EL3600 Size=34G Sync=160 Bus=16 HD0

It is not recognized by fdisk as a single drive under BSD 5.1 setup. It is recognized as da0 and da1, one of which contains 36G and the other contains 20G. The descriptions are as follows:

da0
2432 cylinders/255 heads/63 sectors = 39070080 sectors 19077MB

da1
4494 cylinders/255 heads/63 sectors = 72196110 sectors 35252 MB

Similarly, under Gentoo Linux 1.4 setup's fdisk two disks are identified (not one!): /dev/sda and /dev/sdb

What's going on here? How do I get one drive to be one drive on fdisk?

Thanks,

Bob

Both BSD and Linux seem to recognize your Hitachi drive correctly as the first device on the SCSI chain of devices. The question in my mind is where are these operating systems getting the second address from? Do you have any other SCSI devices? Do you have a CD set up on a scsi-ide interface?

If there are no other physical devices on the SCSI chain then maybe the second disk is a ghost image of the Hitachi disk caused by signals echoing through the wrong wires. Do you have the correct type of SCSI terminator and is it installed in the right location?


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Steve Stites

Thanks for your reply.

Well, I'm not sure Linux is accurately identifying it as "the first drive" as fdisk /dev/sda replies the disk is a 20G disk and fdisk /dev/sdb identifies the true disk as 36G. The setup is as follows. I have three CRU ultrawide SCSI dataports in the machine. The other two drives have had their power shut down so they shouldn't be recognized at all. The messages on bootup only mention the Hitachi drive as HD0. Could it be a bad drive?

Bob

What about the terminating resistor? The last device on the chain needs a terminating resistor so that signals do not bounce back and echo into the computer. And you cannot have a terminating resistor on any device other than the last one physically on the chain. Usually a SCSI device is sold with the terminating resistor set on. So you may have two terminating resistors on the chain, the old one and the one on your new Hitachi disk. Or you may have only one terminating resistor and it is in the wrong spot. Or you could have no terminating resistors and be getting echoes that mimic a non existant disk.

Another possible termination problem is "active termination". An active terminator requires power. So if you are using active termination and the terminating device is powered off then you have no terminator and could get echoes.

Each device on a scsi chain also needs to have a unique address setting. Since you only have one device powered up on your scsi chain I do not think that this is the immediate problem.

"as fdisk /dev/sda replies the disk is a 20G disk and fdisk /dev/sdb identifies the true disk as 36G."

I don't know why there is this difference in addressing between BSD and Linux.


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Steve Stites

I discovered what the problem was. I replaced the SCSI cable and terminator with one from Cables to Go and had the same problem. Then I noticed that behind my monitor in an out of the way, forgotten spot was a USB Peerless drive ,19G, that was attached to the box via the back of the machine. I had had this drive for some time and was using it with a Windows partition on another drive. I disconnected the Peerless USB interface drive and the scsi ghost drive disappeared from BSD and Gentoo's fdisk utilities.

I had forgotten that *nix OSs see USB drives as SCSI drives.

Thanks for your previous comments!