Volume not showing

I upgraded to el capitan a couple of days ago and when I turned my macbook pro on this evening, my media volume, which is on a second drive didn't appear. when this happened in mavericks I just verified and repaired it in disk utilities but that no longer works. any help much appreciated?

the first dumb question is have you unplugged the cable form both ends at the same time?
so taken the cable out of the mac pro and the drive as I am assuming this is an external drive.

If an external drive have you tried swapping out cables?

lastly you can go into terminal and detect drives and force mount the old school way.

http://osxdaily.com/2013/05/13/mount-unmount-drives-from-the-command-line-in-mac-os-x/

no it's an internal drive in a caddy instead of my dvd drive and I'll try the terminal after work

If it is in one of the rear two slots on the old style Mac Pro Towers you may have a failing drive. we had one tower that killed 2 drives in the rear drive caddy location.

it could also be lose and making a bad connection with the SATA controler.

It's a MacBOOK pro and the drive seems to be fine but the volume with all the data seems to be gone

when you say the drive is fine but the volume is gone, do you mean that Disk utility sees the drive but not the volume, because if thats the case then you need to use disk warrior or other disk recovery tools to get your data back.

yes that's what I mean and thanks