Grid computing and blockchains

Grid computing. A grid is a network of geographically dispersed, heterogeneous computing resources, called nodes, that temporarily come together to solve one large task, acting like a virtual supercomputer with huge processing power and storage.

• Countless devices, from phones to workstations, are online, so it is economical to reuse their memory and processing power; grids solve heavy scientific problems without buying costly hardware.
• Unlike the cloud, which focuses on providing services (an IaaS provider rents infrastructure to users), a grid is application-specific: many nodes join together to solve a common problem.
• Two types: data grid (managing large, distributed data with multi-user access) and CPU (processor) grid (moving processing between PCs, or splitting a big task into subtasks for parallel processing).
• Grids need middleware; the open-source Globus toolkit is one, with tools for security, resource and data management, communication and fault detection.

Blockchains. Traditionally, transactions are stored in a central database (as at ticket-booking sites or banks), which can be hacked or lost.

• A blockchain is a decentralised, shared database: every participating computer (node) receives a full copy.
• A block is a secured chunk of data or a valid transaction. Its header is visible to every node; only the owner can see its private data. Blocks link into a chain.
• It keeps one updated, secure, 'append only' open ledger, updated only after all nodes authenticate a transaction: a request is broadcast to all nodes, verified, and only then added as a new block.

Uses: digital currency (the most popular); healthcare data sharing for better diagnosis and care; land registration records to avoid ownership disputes; voting systems to stop vote alteration; and banking, media, telecom, travel and hospitality, and governance, for transparency, accountability and efficiency.

Example (new): a group of farmers' co-operatives recording every sale of milk on a shared blockchain could each check the same record; no single dairy could later change an entry to show it paid more than it did.