Sun Microsystems Sun StorageTek 5800 - Manual (Page 18)

Read-Multiple (WORM) archive. Each object corresponds to a single stream of data and a
single set of metadata; there are no “grouped objects” or “compound objects” other than by
application convention.
Each object corresponds to a single stream of data and a single set of metadata. There are no
“grouped objects” or “compound objects” other than by application convention. Similarly,
there are no “links” or “associations“ from one object to another. The customer application is
shielded from all details of how or where the object is stored. Internally, the actual location of an
object might change over time, or several objects might even share the same underlying storage.
The customer application can retrieve the object without knowing these details.
A stream of data is stored in the object archive using storeObject. Once stored, each such
object is associated with an object identifier or objectid (OID). The storeObject operation takes
both a stream of data and an optional set of user metadata information and returns an OID. The
OID can be remembered outside of the 5800 system and may later be used to retrieve the data
associated with that object using the retrieveObject operation.
Every object has metadata whether or not user metadata was supplied at the time of the store.
For example each object has system metadata that is system assigned and can never be modified
by the user. The OID is associated with the metadata record that represents this object as a
whole; the metadata record is then associated with the underlying data:
OID
↔ Metadata Record → Underlying Object Data
The retrieveObject operation takes an OID as input and returns a stream of bytes as output
that are identical to the bytes stored during the storeObject operation. Both the storeObject
and retrieveObject operations handle the data in a streaming manner. Not all of the data need
be present in client memory or in server memory at the same time, which is a crucial point for
working with large objects.
For the 5800 system Release 1.1, data sizes up to 400 GBytes are tested and supported. Using
sizes even smaller than this may be appropriate as a best practice. For more information, see
Chapter 5, “Programming Considerations and Best Practices.”
From within a customer application, the storing of an object into the archive is an
all-or-nothing event. Either the object is stored or it is not; there are no partial stores. If a store
operation is interrupted, the entire storeObject call fails. Once an OID is returned to the
customer application, the object is known to be durable. In the event of an outage that causes
some data loss, the system should be no more likely to lose a newly stored object than any other
object. There is no way to tie together two different store operations so that both either succeed
together or fail together.
Note – A stored object may or may not immediately be queryable. For more information, see
“The 5800 System Query Integrity Model” on page 21 .
5800 System Overview
Sun StorageTek 5800 System Client API Reference Manual • June 2008 18