I am working with an EMC XtremIO storage array that utilizes SSD devices that use a native 4 KB sector size instead of the traditional 512 B size. I am attaching an IBM AIX 7.1 server to the array. I had trouble getting AIX to assign a PVID to the LUNs and use them in a volume group until I changed the LUNs to emulate a 512 B sector size. As I understand it, there are benefits to using the native sector size if at all possible. Is there a way to get AIX to use these Advanced Format disks with their native sector size?


If you're using jfs, you should have no problem using a 4k block size. Usually, this stuff is taken care of by the multipath driver for the storage, as well as host emulation sometimes. Set your EMC storage's host emulation to "AIX" and make sure you installed whatever drivers they provided for AIX. That'll get everything aligned properly.

  • The problem is with EMC PowerPath (community.emc.com/thread/194945). It only supports 512 B sector size for XtremIO in the current version. Thanks for the quick reply. – Mike Brickl Nov 11 '14 at 17:19
  • Using 512B when your storage works in 4k blocks means that any small IO might waste as much as three quarters of the block and do four times as many IOs as needed. That said, people tend to underestimate exactly how much of their IO is literally single block non-contiguous. Even random IO databases tend to do IO in clumps. Many small random clumps, but not always single 512B transactions. – Basil Nov 11 '14 at 18:56

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