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I have a OWC Mercury Elite 2-bay USB drive enclosure (OWCMEPT934AL2C). I have it set on "individual" settings for the disks, so the 2 disks show up as two separate drives on my Mac (no raid, or spanning). I'm trying to mount them on my slackware file server, but I can't seem to get both drives to mount.

The unit shows up as a single USB device in /dev and it seems to get a drive path assigned (/dev/sdh). When I try to mount sdh1 I get "not a valid block device", however, I can mount it by id.

# ls /dev/disk/by-id/

I can't mount the first one (the physical disk), but the "-part1" device does mount and it is the "top" disk in the unit (the one connected via cables, not directly to the board) - all the correct files are there.

# mount /dev/disk/by-id/usb-OWC_Mercury_Elite-AL_ABCDEF0123451446-0\:0-part1 /mnt/usbdisk1/
# mount
/dev/sdh1 on /mnt/temp/tv type ntfs (rw)

Update 1: When I remove the top disk from the enclosure and reattach it to the system, I get the exact same device show up in /dev/disk/by-id, but when I mount it, it's the lower disk. After trying a few configurations, it seems that the top drive takes precedence over the bottom one. I can always mount a single disk, but never both, and the only way to mount the lower disk is to remove the top one.

Update 2: With some suggestions from a friend, we figure this must be something to do with the driver in linux not supporting multiple disks on the particular controller in the OWC enclosure. So I hooked it back up to my Mac to try and figure out which controller is there. The enclosure shows up on the USB tree in the System Info app as "OWC Mercury Elite-AL Pro RAID" - BUT... there is only one Volume showing up below it - the "top" disk. The lower disk doesn't show up in the device tree anywhere, so the System Info app doesn't see it either. The Mac OS Disk Utility does see the second drive and it mounts no problem. Mac OS also seems to be assigning both drives a unix device path (/dev/disk4 and /dev/disk5).

The unit is a OWCMEPT934AL2C - does anyone happen to know what chipset this thing uses? It is probably an Oxford.. I just don't know what. If I can find that, I'm hoping I can find a driver for it.

Output of lsusb as requested:

# lsusb
Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 003: ID 0557:2221 ATEN International Co., Ltd 
Bus 001 Device 004: ID 0781:5530 SanDisk Corp. Cruzer
Bus 002 Device 003: ID 051d:0002 American Power Conversion Uninterruptible Power Supply
Bus 002 Device 005: ID 0926:000a 

There doesn't appear to be a name, but the last device (005) is the drive becuase it's not there when I run lsusb without the drive connected.

I know this can be done in linux because I have a CloutFTP device that runs an embedded linux, and it sees the 2 drives perfectly, same with my ddwrt router - This is why I'm suspecting the chipset driver.

Anyone know how to get to the second drive? I've been digging around on google, but I can't seem to find a solution.. now after 24 hours, this post is the top hit :(


PS: Been on the support chat with OWC and even they are looking to this post for an answer. I'm hoping someone with a deeper understanding of how linux detects drives will be able to help us out.

share|improve this question
Post the output from lsusb showing the device details. – Michael Hampton Oct 15 '12 at 0:25
Version of Slackware and kernel? The lsusb from ddwrt for comparison might also be useful. – Skaperen Oct 16 '12 at 1:27
It's actually unraid - so it's a slightly bastardized version of Slackware. In my digging, I'm starting to suspect that might matter more then I originally thought. It's linux kernel 3.4.11.. not sure which version of slackware it's based on though. – whiteatom Oct 16 '12 at 2:16
Hmm.. So I didn't have lsusb on my router, so I have attempted to install it, and I think I have now bricked it. :( I'll work on that tomorrow. – whiteatom Oct 16 '12 at 2:39
Yeah.. router is done :( It will involve soldering on the board to recover it.. and a new router is only $100. – whiteatom Oct 16 '12 at 22:07

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