We recently were required to hard set our HBA speed on the adapter to 8 GB , We had an older, slower storage array EVA 8300 that was autonegotiating at 4 GB, we implemented new IB storage that now had the ability to handle 8 GB, with compatible fiber switches we are able to handle the speeds and management and the storage team required that we set the hba speed. I personally would have left it to autonegotiate, but there really is no downside to doing it this way either.
Here are the steps... This is for the Qlogic QLA2562 cards, the process is the same for LSI and other manufacturers, just need to look at their websites and determine the key combination at startup to enter the bios of the card. You can also use SAN SURFER in the full version of ESX with a service console, to perform the task without rebooting, but not on ESXi .
1. Boot the host. When the QLogic banner appears, press CTRL-Q to enter the Fast!Util menu. 2. Select Configuration Settings from the Fast!Util Options menu.
3. Select Host Adapter Settings from the Configuration Settings menu.
4. Select the Data Rate setting and press ENTER.
5. Select the appropriate speed for the device to which the QLA23xx HBA will connect. The options are 0 for 1GB/s, 1 for 2GB/s, ....etc.
6. Press ESC to return to the Fast!Util Options menu.
7. When prompted to save the changes made to the current adapter, select Save Changes.