When SSDs first began shipping in consumer products, there were understandable concerns about their longevity. Time, steadily improving manufacturing techniques, and some low-level OS improvements have all contributed to solid-state storage’s reputation for durability. With reports praising SSDs as provisionally more reliable than hard drives even under heavy usage, it’s easy to see how people might not see the new Chia cryptocurrency as a major cause for concern.
It is. Chia is first plotted and then farmed, and while farming Chia takes very little in the way of processing resources, plotting it will absolutely hammer an SSD.
It’s been years since we talked about write amplification, but it’s an issue that affects all NAND flash storage. NAND is written in 4KB pages and erased in 256KB blocks. If 8KB of data needs to be replaced out of a 256KB block, the drive will need to read the original 256KB block, update it, write the new block to a different location on the drive, and then erase the previous block.
Write amplification has been a problem for NAND since the beginning and a great deal of work has gone into addressing these problems, but Chia represents something of a worst-case scenario. Here’s an excerpt from a recent Chia blog post:
Generating plot files is a process called plotting, which requires temporary storage space, compute and memory to create, sort, and compress the data into the final file. This process takes an estimated 256.6GB of temporary space, very commonly stored on SSDs to speed up the process, and approximately 1.3TiB of writes during the creation.
The final plot created by the process described above is only 101.3GB. There appears to be an order of magnitude of difference between the total amount of drive writes required to create a Chia plot and the storage capacity said plot requires when completed.
Here’s what this boils down to: A lot of consumer SSDs are really bad choices for mining Chia. TLC drives with SLC / MLC caches are not recommended because they offer poor performance. Low-end and midrange consumer drives are not recommended, because they don’t offer high enough endurance. You have to be careful in which SKUs you purchase and enterprise and business drives are more highly recommended in general.
Do not buy a QLC drive to mine Chia.
Optane would seem to be a near-perfect match for Chia, given its much higher endurance, but I can’t find any information on whether people have tried deploying it in large enough numbers to have some idea of what performance and endurance look like under the 24/7 load Chia plotters are putting on their hardware. Maybe somebody will put a rig together using it, as much out of curiosity as anything else.
Beyond that, wfoojjaec recommends users not attempt to plot Chia on any SSD they aren’t comfortable with losing, and not to buy an SSD for the purpose unless you don’t mind throwing it away if it dies much more quickly than expected. Chia plotting is a worst-case scenario for SSD longevity and it should be treated as such.
One note of good news: So far, Chia mining has had a much stronger impact on high-capacity hard drive prices than on SSDs and smaller drives. Hopefully, this continues to be the case.
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