The Netstore Project

Project Description

It is generally agreed that remotely attached storage, using the concept of "Storage Area Networks" (SAN's), is an extremely promising technology for the connection of both disk and tape devices. The basic feature of a SAN, as compared to a conventional IP network, is its support for the direct transmission of low level I/O commands (SCSI) over the network media, thus eliminating the need for intermediate IP based servers, TCP stacks, NFS, AFS, etc. This saves both money and data copies.

However, today's only implementation of a SAN is via Fibre Channel ("FC"), whereas CERN's high speed network installations use Gigabit Ethernet and HIPPI. This project proposes use of a promising "I/O Bridge" technology that will allow access to FC-attached storage via other standard networks as Gigabit Ethernet using GSN as a very high performance backbone.

The Wisconsin company GENROCO is developing such an I/O Bridge to SCSI/FC storage networks. Their current TBF-864 Bridge accepts I/O commands arriving via GSN (Gigabyte System Network) and converts them into SCSI over FC arbitrated loops, to which are attached the actual storage devices. A detail: the GSN I/O is presented in the form of SCSI commands encapsulated in the new ST (Scheduled Transfer) protocol, which is a generic way of carrying SCSI over a new media for which there is no SCSI mapping.

Fig 1: General Overview showing potential use of the Bridge Project

However, to support CERN's strategic move into low-end systems such as Linux PC's, connected to Gigabit Ethernet, a modification is required: a Gigabit Ethernet bridge interface instead of GSN, plus SCSI/ST protocol support to be added to the Gigabit Ethernet driver on the Linux client systems.

The NETSTORE project foresees a demonstration of ST and SAN functionality in autumn 1999 at CERN.

Joint Development Project

Part of the NETSTORE project is the development of a Gigabit Ethernet to GSN interface. The easiest way to do this is as a daughter board to the Genroco TBF-864 bridge. GENROCO and CERN have agreed to join forces in a joint development project to develop a GSN to Gigabit Ethernet bridge, as a natural extension of Genroco's forthcoming family of GSN Switches and Bridges.

Fig 2: Simplified Block Diagram of the Gigabit Ethernet interface

This means that the Gigabit Ethernet part will be an integral part of the TB-864 bridge. The protocol conversion from GSN will be compliant with the IEEE 802.3 standard and with DIX Ethernet. In absence of a standard the conversion will support Jumbo frames according to industry recommendations. Adaptation to a future standard for Jumbo frames is possible.

The development is well advanced by now and it is expected to have working hardware during summer 1999.