Over the past 2 weeks, following the announcement by CoinWallet.eu that they would be “stress testing” the bitcoin network, a few tests appear to have been carried out. CoinWallet’s first test ended up being an epic failure, driving the mempool to a maximum size of 15mb. One week later, they performed a subsequent stress test that managed to delay some transactions for up to 8 hours, although saw the Bitcoin blockchain mempool peak at approximately 25mb.
Many thought that this was the end of the stress tests, however approximately 10 days ago, an unknown entity began a much larger and powerful stress test against the Bitcoin network, driving the mempool to a maximum size of nearly 100mb in unconfirmed fee paying transactions. This created an incredible backlog that resulted in some transactions taking as much as 3 days to receive a single confirmation in the blockchain. It also led to numerous transactions being dropped, massive double-spend attacks against companies such as Coinbase and Shapeshift, and resulted in numerous websites crashing for hours at a time, including blockchain.info.
It now appears that the stress test has once again concluded, with the mempool returning to a normal size. The concern that some users have is that another stress test will occur, which may be larger or more powerful than the stress tests of the past. A 100mb mempool was a major hassle for many Bitcoin businesses, however if the mempool were to reach an even larger size, it is completely possible that nodes could begin crashing, and the worst case scenario of a “hard landing” could occur.
We have reached out to CoinWallet.eu, and they have noted that they will be performing a stress test again in the near future, however their hope is to collaborate with others who are willing to help make a larger impact. According to a CoinWallet representative, the stress tests have proven effective thus far, and have demonstrated that the network is able to handle a vast number of transactions if the block size is increased to accommodate the extra data. They also noted that many companies have improved their software based on the tests, and now are able to offer their clients fluctuating miner fees based on the current network congestion.
Overall, this likely isn’t the end of stress testing and may be the beginning of one of the largest challenges that Bitcoin has seen to date.
Jul 21, 2015