Free tutors on Storage network attached block storage Block storage aggregation in a storage device: Network attached block storage with metadata and File server controller: NAS heads

Free tutors on Storage network attached block storage Block storage aggregation in a storage device: Network attached block storage with metadata and File server controller: NAS heads

 Multi-site block storage file servers File server controller: NAS heads

The connection from storage to host via a storage network can be represented in the Shared Storage Model as shown in Figure 10.12. In this case:

• Several hosts share several storage devices.

• Block-oriented protocols are generally used.

• Block aggregation can be used in the host, in the network and in the storage device.

 Block storage aggregation in a storage device:

SAN appliance Block aggregation can also be implemented in a specialized device or server of the storage network in the data path between hosts and storage devices, as in the symmetric storage virtualization (Figure 10.13, Section 5.7.1). In this approach:

• Several hosts and storage devices are connected via a storage network.

• A device or a dedicated server – a so-called SAN appliance – is placed in the data path between hosts and storage devices to perform block aggregation, and data and metadata traffic flows through this.

 Network attached block storage with metadata

server: asymmetric block services The asymmetric block services architecture is identical to the asymmetric storage virtualization approach (Figure 10.14, Section 5.7.2):

• Several hosts and storage devices are connected over a storage network.

• Host and storage devices communicate with each other over a protocol on block level.

• The data flows directly between hosts and storage devices.

• A metadata server outside the data path holds the information regarding the position of the data on the storage devices and maps between logical and physical blocks.

 Multi-site block storage

Figure 10.15 shows how data replication between two locations can be implemented  means of WAN techniques. The data can be replicated on different layers of the mo using different protocols:

• between volume managers on the host;

• between specialized devices in the storage network; or

• between storage systems, for example disk subsystems.

If the two locations use different network types or protocols, additional converters can be installed for translation.

 File server

A file server (Section 4.2) can be represented as shown in Figure 10.16. The following points are characteristic of a file server:

• the combination of server and normally local, dedicated storage;

• file sharing protocols for the host access;

• normally the use of a network, for example, a LAN, that is not specialized to the storage traffic;

• optionally, a private storage network can also be used for the control of the dedicated storage.

 File server controller: NAS heads

In contrast to file servers, NAS heads (Figure 10.17, Section 4.2.2) have the following properties:

• They separate storage devices from the controller on the file/record layer, via which the hosts access.

• Hosts and NAS heads communicate over a file-oriented protocol.

• The hosts use a network for this that is generally not designed for pure storage traffic, for example a LAN.

• When communicating downwards to the storage devices, the NAS head uses a block-oriented protocol.

NAS heads have the advantage over file servers that they can share the storage systems with other hosts that access them directly. This makes it possible for both file and block services to be offered by the same physical resources at the same time. In this manner, IT architectures can be designed more flexibly, which in turn has a positive effect upon scalability.