📄️ Reliability of Storage Devices in Chia Farming
Chia is an extremely light workload compared to typical end-user workloads, 0.37% of the lowest HDD rated workload limit of 200TB/year. It is also 309 times lower disk busy time than an example hyperscale data center workload. Plot files contain random cryptographic hashes that can easily be created with no user data, removing data durability requirements for data storage in Chia farming. Hard drives, SSDs, or any consumer electronic device, don’t have a rated lifetime, reliability is measured in the annual failure rate or mean time between failure. They do have a warranty, most often 5 years which is used for most LCA (life cycle assessments). SSDs also have a rated endurance measured in host writes, TBW (terabytes written). HDDs have a rated workload in TB/year for both reads and writes, due to mechanical wear on the drive.
📄️ SSD Endurance
The fastest plot creation is done completely in memory, but requires a server with a large amount of DRAM to perform this. Most consumer plotters are using an SSD as temporary storage to perform plotting. Mainstream SSDs today use NAND flash technology to store data. NAND is high performance, scalable, and low cost - warranting the use in virtually every computing segment from mobile phones, SD cards, consumer laptops, and data centers. However, NAND must be erased before the cell is programmed, a process known as a program erase cycle, and can only be performed a certain amount of times before the NAND cell wears out and can no longer reliably store user data. This is defined generally as an SSD no longer meeting the UBER (uncorrectable bit error rate), retention time (how long the device can store user data safely while powered off, at a given temperature), or functional failure (device can no longer power on). The metrics to measure endurance of an SSD is defined in Terabytes Written, or TBW, at a certain workload. The workload defined is generally the JESD219 workload from JEDEC organization. An SSD can still plot well beyond meeting it's rated TBW limit, because UBER can be measured (when seeing host errors) and retention is not required (Chia plotting requires temporary or ephemeral storage).