.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 (see
<<struct-lu-fid>>) that identifies both the OST on which it resides as
well as the object identifier itself.
****