A new cryptocurrency, Chia, has cultivated many discussions about the storage needs associated with Chia Network’s blockchain. While Chia farming relies heavily on hard disk drives (HDDs), high-performance solid state drives (SSDs) also play a vital role. However, since Chia’s write-intensive protocol can be problematic for most commercial SSDs, it’s important for would-be farmers to understand the facts before deciding to start seeding plots. First, a brief explanation of how Chia differs from other cryptocurrencies will help us understand these unique challenges.
Chia Network was founded by Bram Cohen, who also created the BitTorrent network. While cryptocurrencies like Bitcoin operate under a proof of work algorithm, Chia works on a proofs of space and time model to utilize unused disk space. Chia Network describes itself as builders of a decentralized blockchain and smart transaction platform with increased efficiency and security. Chia’s Green Paper says the older proof of work algorithm “wastes massive amounts of energy and is less secure against mining centralization.”
Proofs of space and time
You can think of proofs of space as a way to prove that you are setting aside unused space on your HDD for farming Chia. Proofs of time refers to the period needed to pass between blocks. A verifiable delay function (VDF) implements the proof of time during Chia farming. It takes a certain amount of time to compute but is fast to verify. An essential characteristic of VDF is that it requires sequential computation, which means that running multiple parallel machines has no benefit. That potential waste of electricity is considered minimized, which is how Chia positions itself as a green alternative to other cryptocurrencies.
Chia Network’s use of agricultural analogies are intentional. Deleting your disk drives is like clearing a field. Installing the Chia software on an HDD is called seeding Chia blockchain. Users are called farmers, who store cryptographic numbers into plots and then wait for their crops to grow. When a blockchain broadcasts a challenge for the next block, farmers can scan their plots to see if their hash matches (or comes closest to matching) the challenge. If it does, that makes it harvest time.
If the process sounds like playing the lottery, it’s similar. A farmer’s probability of winning a block is based on the percentage of total space they are plotting compared to the entire network — which is growing every day. As more farmers get involved in Chia, the probability of winning a block decreases.
Solid State Drives
Central to farming Chia is the need for storage space. Generating plot files (plotting) requires temporary storage space, compute, and memory to build, sort, and compress data into a final file. Farmers generally use SSDs to speed up the process before eventually moving the compressed data to HDDs while they grow. Because plotting is a write-intensive process, farmers were quick to realize that SSD endurance is a serious consideration. Since consumer SSDs are optimized for lighter workloads, they are not suitable for Chia plotting. Instead, the Chia team advocates the use of data center SSDs, which have higher endurance rates.
Even though data center SSDs are better suited for Chia farming, they can be difficult to purchase, since they are not typically sold directly to consumers. This might tempt some farmers to go ahead and use consumer SSDs. A simple cost-benefit analysis should discourage this temptation.
“...Don't plot with consumer SSDs! Or at least, only do a little bit of plotting with each consumer SSD. Also don't clean nonstick pans with steel wool, don't clean vegetables with soap, and don't use your phone as a doorstop. These aren't arguments against steel wool, soap, or phones, they're basic guidelines about using your tools properly.” — Bram Cohen, Chia Network founder