Buyer Beware: Chia Miners Are Selling Worthless Second-Hand SSDs
Most of the time, the PC used market is a pretty good place to find reasonable hardware deals. I’ve bought a fair amount of used and refurbished hardware in my life and had few complaints about the experience overall. The modern cryptocurrency market, however, has changed things somewhat.
Recent news regarding the Chia cryptocurrency should have would-be eBayers on alert. As the price of Chia has cratered, many people are dumping their plotting and mining rigs on auction sites. Here, there’s an important distinction: Because plotting is computationally and storage intensive, while storing plots is not, most people plotted on fast SSDs and farmed their plots on hard drives.
A hard drive that’s been retired from Chia farming is almost certainly in perfect condition. Data may have only been written to drive once, or at most a handful of times. An SSD that’s been used for Chia mining, on the other hand, should be assumed to be a dead drive running.
A post from VNExpress.net notes that Chia miners are dumping drives now that prices have fallen and quotes a shop owner in Ho Chi Minh City who claims the average SSD lifespan when used for Chia plotting is approximately 80 days, compared with as much as a decade of normal usage. That kind of longevity hit is not unexpected, because Chia is designed to write far more data during the plotting process than is actually stored on the drive in the final plot. If wear-leveling is the process of spreading writes across the drive to avoid early wear in any given location, writing far more data during the plotting process than the size of the eventual plot is more-or-less the reverse. It might be possible to write an application that was even harder on SSDs deliberately, but the author would have to work at it. This Chia blog post gives some data on how large the discrepancy is:
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.
Buying new is going to be safer than trusting the used market for SSDs for a little while, but let’s say you’re low on cash but prefer a used SSD over a used spinning disk. In this case, ExtremeTech recommends the following two-step process:
1). Ask the seller for some basic information on the drive, if the auction doesn’t provide it. When was it purchased? What was it used for? Can the seller provide photos of the drive running an application like CrystalDiskInfo and give you the SMART data before purchase? (This may not be particularly likely, but it never hurts to ask).
2). Upon receipt, chuck the drive into your system and fire up the reporting tool of your choice. There are a lot of utilities that can give you a basic report on your drive’s SMART status, including CDI. Here’s what a report on a Crucial MP600 2TB test SSD looks like:
This drive has written ~60TB of data throughout its lifetime and has been powered on 9,963 hours. Chia didn’t launch until last May, so any drive bought new and used for Chia mining is going to have a much smaller number of power-on hours. Given that 80 days is actually a longer lifespan than we’ve heard in the past for an SSD plotting Chia, we’d expect Chia mining drives to have a very high ratio of TB written per hour of activity.
This is not a perfect, fool-proof method, but most SSDs should have a relatively low number of drive writes. Even if you’re a gamer who filled an entire 2TB drive with Steam and EGS titles, you probably don’t delete and rewrite those titles on a weekly basis. The number of full drive writes an SSD is specced for varies by drive, but a huge amount of data written in a time period that works out to just 60-120 days of usage should be viewed with suspicion, especially if the seller did not disclose any usage patterns that would write so much data to the drive.
For now, ET recommends you try to buy new SSDs instead of used whenever possible. If you do buy used, checking the SMART data on the drive should at least give you a heads-up on whether you were lied to before the SSD fails. SSDs used for plotting Chia cannot be trusted to remain functional for any length of time and should not be trusted for mission-critical data. Hard drives used for farming should be fine and it’s not clear if anyone ever actually tried plotting on hard drives given their low performance.