Write a short note on DAFS.
1 Answer

The DAFS is a newly developed NFS that is tailored to the use of RDMA. It is based upon NFS version 4, requires VI.

DAFS makes it possible for several DAFS servers together to provide the storage space for large files system. It remains hidden from the application server.

The communication between DAFS client and DAFS server generally takes place by means of RDMA. The use of RDMA means that access to data that lies upon a DAFS server is nearly as quick as access to local data. In addition, typical file system operations such as the address conversion of files to SCSI block address, which naturally also require the CPU, are offloaded from the application server to the DAFS server.

enter image description here

enter image description here

Figure: (1) The DAFS client communicates with just one DAFS server. (2) This processes file access, the blocks of which it manages itself. (3) In the case of data that lies on a different DAFS server, the DAFS server forwards the storage access to the corresponding DAFS server, with this remaining hidden from the DAFS client.

An important function of file sharing in general is the synchronisation of concurrent access to file entries - that is, metadata such as file names, access rights, etc. - and file contents, in order to protect the consistency of the data and metadata. DAFS makes it possible to cache the locks at the client side so that a subsequent access to the same data requires no interaction with the file server.

If a node requires the lock entry of a different node, then this transmits the entry without time-out-DAFS uses lease-based locking in order to avoid the permanent blocking of a file due to the failure of a client.

Furthermore, it possess recovery mechanisms in case the connection between DAFS client and DAFS server is briefly interrupted or a different sever from the cluster has to step in. Similarly, DAFS takes over the authentication of client and server and furthermore can also authenticate individual users in relation to a client-server session.

Please log in to add an answer.