Public versus Private Blockchains for Storage

One of the storage array features that is beginning to gain traction is integrated private blockchain. Nexsan has announced, for example, that it has added private blockchains (and RDMA over Converged Ethernet support) to version 8.3 of its Assureon solution. When comparing public versus private blockchains, does the “private” factor make blockchain technology a good bet for your next storage appliance?

The first thing that must be understood about private blockchains is that the technology is significantly different than public blockchains. Public blockchains, which are often referred to simply as blockchain, first gained notoriety for their role in enabling cryptocurrencies such as Bitcoin. Blockchains store transactions in an immutable and widely distributed ledger that has thus far been immune to manipulation.

Public blockchains are based on a public, peer-to-peer network in which each peer acts as a node. Each node includes a copy of an append-only ledger. This means that transactions can be written to the ledger, but previously existing transactions within the ledger cannot be removed or altered. Each transaction has a mathematical relationship to the previous and next transaction, therefore ensuring the integrity of each transaction.

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Interestingly, some of the very things that make public blockchains so appealing also render them undesirable for use in most enterprise storage applications.

One of the things that helps to maintain a blockchain’s integrity is the public node model. When data within the blockchain needs to be validated, a quorum of nodes form a consensus as to whether a particular item is valid. The inner workings behind this process can vary from one blockchain to the next, but, generally speaking, each node uses its own copy of the blockchain data to make a determination as to whether an item is valid.

The fact that each blockchain node has its own copy of the data means that there is no centralized database for an attacker to compromise. The disadvantage to this approach is that it is relatively slow. After all, the various nodes each have to perform their own queries, make a decision and then cast a vote. Those votes are tallied to make a go/no-go decision. This intricate process takes time to complete. Some public blockchains are estimated to perform fewer than a dozen transactions per second, thus rendering the process totally inadequate to meet the demands of a high-performance enterprise database.

The other major problem with public blockchains (at least from an enterprise standpoint) is that they are transparent. Blockchain technology is based on the idea that the transparency of data helps to ensure its integrity. As such, anyone can set up a node and join a public blockchain. It doesn’t matter that the node is untrusted. And because the blockchain data is public, it is relatively easy to mine the blockchain data.

When comparing public versus private blockchains, the context shifts significantly. Private blockchains seek to maintain the basic essence of blockchain technology, but in a way that makes them better suited for use in the enterprise than public blockchains. Like its public counterpart, private blockchain is based on a collection of nodes operating within a peer network to ensure the integrity of the data.

Private blockchains use an append-only model that is very similar to that of public blockchains. When comparing public versus private blockchains, however, private blockchains do not allow random, untrusted nodes to join and participate in the peer network. Instead, the nodes are owned by the organization and presumed to be trustworthy.

In the case of storage appliances with integrated private blockchains, the storage appliances would presumably work together to form the required peer network, with each node retaining its own copy of the blockchain data. Because an organization owns all of its own blockchain nodes, the blockchain data is not transparently disclosed to the public, which is hugely important for organizations wishing to keep their data private.

In addition, there is high-speed connectivity available between the private blockchain nodes (or storage appliances, in this case). That connectivity and the limited number of nodes combine to allow the private blockchain to perform far more transactions per second than what a public blockchain could realistically be expected to handle.

Some critics have stated that when comparing public versus private blockchains, private blockchains are less secure because of the centralization of the nodes. At the same time, though, the private blockchain nodes are deemed to be trustworthy because they are under an organization’s direct control.

Private blockchains are not going to be suitable for every organization. For those that do need a blockchain solution, but also wish to keep data private, purchasing storage arrays with integrated blockchain capabilities can be a compelling alternative to a more conventional approach to building private blockchains.