These recommendations are there to prevent issues with unaligned IO and represent different pieces of a larger puzzle.   XtremIO 3.x and newer has been optimized to process IO that is 8K or 8192 bytes. The minimal IO size it can receive is 512 bytes - this value is configured during the creation of the LUN on the XtremIO array.
Customer is asking :  Connecting our Xtremio 4.0.2-80 to some of our Solaris 11.3 sparc systems.  I have some questions on the setting that are to be changed.  The instructions state to set the physical-block-size to 8192 but then later it says to use 512 when you create the volumes.  Is this correct. What purpose does setting the physical-block-size do.? _______________________________________________________________  From the Host Guide I found:  – For a SPARC host: Append the following line to the /etc/driver/drv/ssd.conf file: ssd-config-list = "XtremIO XtremApp", "throttle-max:64, delay-busy:30000000000, retries-busy:90, retries-timeout:30, physical-block-size:8192, retries-notready:30"; - physical-block-size:8192 - The block size used on the storage system. For XtremIO versions3.x (or above), use 8192. Otherwise, use 4096. Note: This setting is only relevant for Solaris 11.   Also found :  *using a physical block size other than the default 512 bytes can result in incompatibilities when using some layered clustering products. Using the default 512 byte physical block size, as defined in the sd/ssd.conf file, alleviates this problem.  so what is the best practice to recommend the customer to configure.? 
What purpose does setting the physical-block-size do?