sas hp 6250 not found

Does Windows see the tape drive in Device Manager?
If not, have you verified that this combination of HBA, cable, and tape drive can be seen in another server?
Was this a tape drive purchased as a standalone drive, or was it a pull from a tape library put into an external enclosure?   What is the specific tape drive model number?
Is the HBA HP's branded card, or did you buy some other LSI card said to be equivalent to the HP models you listed?
If the drive is seen in Windows' Device Manager but not by Yosemite, I'd recommend you download HP's free Library and Tape Tools and see if it can discover the drive and run diagnostics on it.  http://h18006.www1.hp.com/products/storageworks/ltt/index.html

Does Windows see the tape drive in Device Manager? No
If not, have you verified that this combination of HBA, cable, and tape drive can be seen in another server? Not able to test at this time, no spare server
Was this a tape drive purchased as a standalone drive, or was it a pull from a tape library put into an external enclosure?   What is the specific tape drive model number? new HP LTO-6 Ultrium 6250 half height external tape drive from ebay seller with warranty.
Is the HBA HP's branded card, or did you buy some other LSI card said to be equivalent to the HP models you listed? a separate ebay seller said it was an hp card but it says pci express lsi corp 2006-2007 500605B 0-018F-8040 mic lsi-3801e (B)
If the drive is seen in Windows' Device Manager but not by Yosemite, I'd recommend you download HP's free Library and Tape Tools - not seen in device manager or yosemite. tape drive seller refuses to recommend a hba card. he did recommend a cable.  HP Tape Tools says zero devices attached.

The controller is supposed to support tape, so that's a good thing.

Just in case, make sure that the HBA has the latest drivers.  This is a relatively old card, and I see newer firmware as late as 2011.  (Is the HBA seen by Windows?)

Other than testing a different adapter and cable (in case one of them is bad), and testing the adapter in a different system, I don't know what to tell you.  DIscovery of a tape drive in Windows should be relatively simple

This setup works in a server2008.
I just took delivery of another lenovo td340 with a similar, but older model tape controller pre-installed.
I bought the same model sas hba for my problem customer and essentials doesn't see it. Why?

Someone mentioned firmware?

You can update the firmware in an HP ProLiant server (all necessary firmware) by using the HP ProLiant Support Pack, info and links found at PSPPSP

For individual products/HBAs, go to hp.com/go/support and click on "Drivers / Downloads", enter your model and OS and off you go.

You can also use HP Library and Tape Tools (link above) to run diagnostics and possibly upgrade HBA and drive firmware.

The fact that this one card wasn't recognized and an identical one was, though, seems to indicate it may be a bad card.   Have you contacted HP for assist on warranty replacement/

I have to remote in to find the model of the raid 10 card
for tge external tape drive,  we've tried 2 sas hba cards, one is known good. the server does not see the hba.
the server is lenovo td340, server 2012 essentials r2 64 bit loaded by lenovo.
no support from hp because card was not bought from then so checking with synnex to see if I buy a card from them, will they support it.
difficult customer to get maint window.

I accept my own comment as no one had said Lenovo TD340 was so proprietary that the existing sas hba Raid10 controller not allow another sas hba controller to be used for tape drive. I spent many, many months talking to HP, Lenovo, IBM before I found the right person who had this knowledge.