Database Reference
In-Depth Information
The problems described above can be summarized with the following four
requirements:
The ability to reserve storage resources (disk, archival storage) dynam-
ically.
The ability to request data to be moved into or copied between storage
resources in a uniform fashion.
The ability to dynamically release storage when no longer necessary.
The ability for storage to be assigned for a given lifetime, and then
released automatically in order to avoid clogging storage or rendering it
useless as it gets full.
We will describe in some detail such a standard approach, referred to as
storage resource management (SRM) in the subsequent sections. The approach
taken is to provide a standard specification that can be implemented with any
storage system. Such implementations of SRMs can target various storage
systems with the goal that all such systems interoperate.
In contrast to the approach of permitting multiple implementations accord-
ing to a standard specification, another approach is a centralized one, such as
the storage resource broker (SRB).
1
SRB provides a single front end, which
interfaces to a variety of back-end storage systems, giving the client the illu-
sion that all data is stored in a single monolithic system. This distinction is
illustrated in Figure 3.1. Another important difference is that SRB is not de-
signed to provide storage space reservations or manage space quotas. However,
since it manages multiple data stores centrally, it can provide the capability
of a metadata catalog for all its holdings. SRB has been used very successfully
Client
User/Applications
Client
User/Applications
SRB Front End
SRM
SRM
SRM
SRB Back End
Storage
System 1
Storage
System 3
Storage
System 1
Storage
System 2
Storage
System 3
Storage
System 2
Figure 3.1
The difference in architecture between SRMs and SRB. SRMs
permit independent implementations to various distributed storage systems
that facilitate space reservation and management. SRB takes a centralized
approach that provides a uniform view of all the data in storage systems, but
no storage space management.
