Last year I spun an Ethereum validator after having used pooled staking for a while. What prompted the action was the desire to contribute to Ethereum network's decentralization and robustness given that I had the hardware and required eth to run a solo staking validator.
It is no secret that Ethereum has a client diversity problem. While the consensus layer diversity has improved over the last year to bring Prysm under acceptable limits, Geth's +80% share as an execution client is absolutely a risk and needs to be addressed.
When spinning up my validator, I chose Nethermind, a minority client, as my execution layer to help diversity away from Geth. Yesterday I woke up to see my validator is offline. A quick check of the logs made it clear that the issue lies with the client and a trip to EthStaker and Nethermind's discord channel confirmed what was going on. A hotfix was released in a few hours and everything was up and running again.
A postmortem is not available yet at the time of this writing, so I do not know how this escaped the testnet and impacted the mainnet directly. Nonetheless, kudos to the Nethermind team for promptly addressing the issue. And a sincere thank you to all the fellow stakers who run minority clients.
This experience sent me looking deeper what could have happened if the same had happened to Geth. To be clear, this is not throwing shade at Geth at all. They are an amazing team of engineers and have done a stellar job. Client diversity is a feature of Ethereum and helps bolster the network's decentralization in one more dimension.
Why is Geth so Popular?
The main reason for Geth's popularity is the heavy usage by pooled / centralized solutions running staking as a service. Aside from having the longest track record, Geth is also a bit lighter on hardware requirements vs other clients. Nonetheless, staking on Ethereum was designed to be accessible for solo stakers and plenty of inexpensive consumer grade hardware can run a full node.
Risks to the Network
Running an Ethereum validator comes with rewards and penalties and while being offline for a few hours wouldn't normally be a big deal, if 1/3 of the validators are offline then the chain wouldn't be able to reach finality and enters an emergency protocol called "inactivity leak". If what happened to Nethermind had happened to Geth, then Ethereum would have entered the emergency protocol and depending on how fast the network recovers, potentially millions of eth could've been wiped out given the quadratic nature of penalties during a majority blackout. While extremely unlikely, a few days of blackout on Geth has the potential to wipe out the entire 32 eth stake of each validator!
Dankard Feist has a great write-up that digs deep into this scenario.
Cost of Being Offline
Normally a validator that goes offline accrues a penalty equal to the amount it would have earned instead. With validator reward hovering around 2.5% at the time of writing, this is nothing to sweat about for a few days. However, if 1/3 of validators go offline, then the chain cannot finalize and quadratic penalties kick in. Other factors such as being in a sync committee might exacerbate the penalty.
It is worth emphasizing that while a full blackout of the network is extremely unlikely, none of us is above Murphy's law. Anything that can go wrong, will go wrong.
What You Can Do
The above sound pretty scary, but here are a few things that mitigate a prolonged blackout (measured in days) that you can do right now to protect yourself and help the network along the way.
Switch Clients - Nethermind, Besu, and Erigon are tried and tested execution clients that can be switched over to right now. Syncing normally takes a few hours with a fast internet connection. In the case of a blackout with other validators offline there will be fewer peer nodes to connect to, but the mechanism is in place. This is the best mitigator and if you run an ethereum node you should diversify away from Geth as soon as possible. In non-centralized staking solutions such as Dappnode, Rocket Pool, or your own hardware, switching client is as easy as clicking a few buttons or running a few command lines.
Solo Staking - The best way to help the network is running a solo staking validator. The hardware requirements are accessible and while 32 eth is a substantial sum, there are a variety of pooled staking such as Rocket Pool you could consider. Staking on centralized exchanges however, while might be the "easy" option is generally not a good idea. As always, not your keys, not your coin.
Exiting Validators - The exit queue has been a few hours long at most for a while now, but you do not need your own node to be running to be able to exit your validator. As long as you have set an exit address (which should have happened when you generated your validator keys), then you can simply use a tool such as beaconcha.in and exit your validator. This helps the network finalize faster and stop your penalties. The queue will surely swell if there is a rush to the gate, but nonetheless an important mechanism in place.
Running 2 Ethereum Nodes - This is more suited to professional setups or if you are running more than one validator. That said, you can run two full nodes and switch your validator over to the functional one, should one go out.
As the saying goes, any decentralized network is only as decentralized as its most centralized part. Geth's supermajority status is a risk to the network that while extremely unlikely can have an effect similar to the DAO fiasco that I think few of us would want to live through again.
If you have the time and the means to run a solo staking validator, consider running a minority client. Not only it is a hugely educational undertaking, it will help bolster the overall network's health, and you will collect financial rewards on your validator as well. Who knows, might even get a juicy MEV-charged block too!