make EUI64 or NGUID support a requirement instead of a SHOULD

As suggested by David Black.

diff --git a/scsi_nvme_middle.xml b/scsi_nvme_middle.xml
index f5e9b8bb47901b38dce556cfbcb5f469d545d9e2..36f589ff4c7481b312b0927dd01c0d2aed1441ae 100644 (file)
--- a/scsi_nvme_middle.xml
+++ b/scsi_nvme_middle.xml
@@ -71,15 +71,19 @@
 
   <section anchor='ssc:volident' title='Volume Identification'>
     <t>
-      The SCSI layout uses the Device Identification VPD page (page code
+      The pNFS SCSI layout uses the Device Identification VPD page (page code
       0x83) from <xref target="SPC4" /> to identify the devices used by
-      a layout.  Section 6.1.4 of <xref target="NVME-STLR" /> explains
-      how an an implementation SHOULD construct a valid Device
-      Identification VPD page based on the NVMe Identify data.
-      Only NVMe devices that support either the EUI64 or NGUID value in the
-      Identify Namespace data SHOULD be used as storage devices for the
-      pNFS SCSI layout, as the methods based on the Serial Number for
-      legacy devices might not be suitable for unique addressing needs.
+      a layout.  Section 6.1.4 of <xref target="NVME-STLR" /> lists ways
+      to build SCSI Device Identification descriptors from NVMe Identify
+      data.
+
+      To be used as storage devices for the pNFS SCSI layout, NVMe devices
+      MUST support either the EUI64 or NGUID value in the
+      Identify Namespace data, as the methods based on the Serial Number for
+      legacy devices might not be suitable for unique addressing needs and
+      thus MUST NOT be used.  If possible NVMe devices uses as storage
+      devices for the pNFS SCSI layout SHOULD support the NGUID value as
+      it is the larger identifier.
     </t>
   </section>