Know more on Asymmetric file services: NAS/file server metadata manager Object-based storage device (OSD)

Know more on  Asymmetric file services: NAS/file server metadata manager Object-based storage device (OSD)

A file server metadata manager (Figure 10.18) works in the same way as asymmetric storage virtualization on file level (Section 5.7.2):

• Hosts and storage devices are connected via a storage network.

• A metadata manager positioned outside the data path stores all file position data, i.e. metadata, and makes this available to the hosts upon request.

• Hosts and metadata manager communicate over an expanded file-oriented protocol.

• The actual user data then flows directly between hosts and storage devices by means of a block-oriented protocol. This approach offers the advantages of fast, direct communication between host and storage devices, whilst at the same time offering the advantages of data sharing on

file level. In addition, in this solution the classic file sharing services can be offere

in a LAN over the metadata manager.

 Object-based storage device (OSD)

The SNIA Shared Storage Model defines the so-called object-based storage device (OSD) The idea behind this architecture is to move the position data of the files and the access rights to a separate OSD. OSD offers the same advantages as a file sharing solution,combined with increased performance due to direct access to the storage by the hosts, and central metadata management of the files. The OSD approach functions as follows

(Figure 10.19):

• An OSD device exports a large number of byte vectors instead of the LUNs used in block-oriented storage devices. Generally, a byte vector corresponds to a single file.

• A separate OSD metadata manager authenticates the hosts and manages and checks the access rights to the byte vectors. It also provides appropriate interfaces for the hosts.

• After authentication and clearance for access by the OSD metadata manager, the hosts access the OSD device directly via a file-oriented protocol. This generally takes place via a LAN, i.e. a network that is not specialized for storage traffic.