LUDOC-296 protocol: Rearrange presentation to be more top-down

[doc/protocol.git] / struct_ost_id.txt

diff --git a/struct_ost_id.txt b/struct_ost_id.txt
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+++ b/struct_ost_id.txt
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+OST ID
+^^^^^^
+[[struct-ost-id]]
+
+The 'ost_id' identifies a single object on a particular OST.
+
+[source,c]
+----
+struct ost_id {
+       union {
+               struct ostid {
+                       __u64   oi_id;
+                       __u64   oi_seq;
+               } oi;
+               struct lu_fid oi_fid;
+       };
+};
+----
+
+The 'ost_id' structure contains an identifier for a single OST object.
+The 'oi' structure holds the OST object identifier as used with Lustre
+1.8 and earlier, where the 'oi_seq' field is typically zero, and the
+'oi_id' field is an integer identifying an object on a particular
+OST (which is identified separately).  Since Lustre 2.5 it is possible
+for OST objects to also be identified with a unique FID that identifies
+both the OST on which it resides as well as the object identifier itself.