I am running the 2.6.25.14 kernel on a RedHat 5.3 X64 bit OS. I am booting off a USB compact flash. When I put two hard drives in a test system the OS does not allow me to access either, however if I have one hard drive inserted I am able to mount the hard drive fine. Extremely strange. When both hard drives are inserted dmesg reports a sde and sdf, it just will not let me access them. I am not sure if this is a hardware issue or OS.

fdisk /dev/sde says unable to open. smartctl -i /dev/sde says NO Medium found. When I boot with only one inserted i am able fdisk. mount, etc... /dev/sde just fine.

The USB controller has 5 slots to insert various media, but I am just using it for its compact flash slot.

Why will the system play nice with one hard drive and not with two?

Check dmesg |tail.
Could be a current issue - overcurrent when the 2 drives are on. The box then switches off the ports. Also check the o/p of
fdisk -l with one and 2 drives attached, to confirm a port issue.
Are the drives identical?

1 members found this post helpful.

I was going the wrong direction. fdisk -l showed the error in my ways. For some reason with one hard drive in the system the SATA drive was sde, but with two the SATA hard drives were sda and sdb. Nothing in dmesg or /var/log/messages indicated this to be the case.

The error in my ways were that I was blindly looking incrementing down the alphabet rather than up sdg, sdh. etc...

Thank you for your time.