How To Estimate the Lifespan of an SSD

There are two key questions we need to ask whenever we buy storage: How fast does it go and how long does it last?

We’ve got a pretty good handle on SSD speeds. SATA SSDs hover around 400 – 500 MB/second. NVMe SSDs range from 950 – 3,000 MB/second, depending upon configuration.

Trickier, though, is determining lifespan; also called “endurance.”

To begin with, SSD lifespan is determined by writes. You can read data from an SSD as often as you want without damage. Wear-and-tear occurs with writes (or erasures, which are simply writes without replacing the old data with new.)

There are two reliable estimates that help determine the lifespan of SSDs:

• TBW (Terabytes Written)
• DWPD (Drive Writes Per Day)

TBW indicates how many total terabytes an SSD drive can write before hardware failure becomes likely. (Remember, reads don’t cause any wear on an SSD.)

The “TBW rating is higher for larger capacity drives as they have more flash memory cells to write. For example, a typical 500GB SSD has a TBW of around 300, whereas 1TB SSDs usually have 600 TBW.

“DWPD… tells how many times you can overwrite the entire [capacity] of an SSD daily for a specific warranty period. So, for example, if your 1TB SSD is rated 1 DWPD, it can handle 1TB of data written to it every day over its warranty period. But if its DWPD is 10, it can withstand 10TB of data written to it daily.

“DWPD is more commonly used in the enterprise space, whereas TBW is typical for consumer-grade SSDs.” (HowToGeek.com)

What TBW means in real-life is that with, say, a TBW of 300, you can write 300 terabytes of data to that drive before failure becomes likely. I’ve seen TBWs range from 30 to over 1,000. Drives with larger TBWs are likely to last longer even under heavy media use.

The problem is that, while these specs are known, they are not always posted to a vendor’s website. Still, if you have the opportunity to compare hardware, picking an SSD with a larger TBW is likely to result in an SSD that lasts longer.

MONITOR YOUR DRIVE

DriveDX, from BinaryFruit, is an excellent utility for monitoring drive health. In this example, my OWC Thunderblade shows 98% life left after heavy use in testing and media production (top red arrow).

The middle section flags problems if they exist on the drive (middle red arrow).

At the bottom, DriveDX tracks each blade in this 4-blade RAID and shows that each blade has only written about 8.5 TB in over a year (bottom red arrow). This impresses me because I’ve used this drive extensively in testing and media editing, yet haven’t begun to wear it out.

CALCULATE TBW AND EXPECTED LIFE

A quick way to calculate the TBW of a drive, if you have DriveDX or similar monitoring software, is to divide the Data Units Written by (1 – % SSD Lifetime Left). In the case of the Thunderblade illustrated in the screen shot above:

8.5 / ( 1 – 0.98 )   = 8.5 / 0.02 = 425 TBW

To turn this into an estimated  lifespan, I put this drive into service the last week of November, 2022. That’s 61 weeks ago. Doing the math:

Current weeks in use / total weeks of lifespan = Current data use / total data over life

61 / X = 8.5 / 425
X = 61 / ( 8.5 / 425 ) = 3,050 weeks = 58 years.

NOTE: As a check to see how closely my estimate was to reality, I emailed OWC who told me: “The 2TB OWC Aura Ultra IV SSD is rated at 1,000 TBW, which works out to recording 392 GB per day for 7 years.”

So, yeah, this SSD RAID has a LOT of life left in it!

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