Two enterprise SSD quotes can look easy to rank: one drive is rated at 1 drive write per day, the other at 0.5. Yet the lower-rated drive may support the same daily volume of writes if its capacity is twice as large. For a data center buyer, the useful comparison starts with the amount of data the application actually writes.
DWPD needs a capacity and a time period
Drive writes per day, or DWPD, expresses a daily write allowance relative to drive capacity over a specified period. Terabytes written, or TBW, expresses a cumulative write quantity. Kingston explains the relationship as TBW divided by capacity and the number of days in the warranty period. Always read the product’s conditions alongside the headline rating. Kingston’s endurance guide provides the definitions and formula.
Normalize the quotation before choosing a drive
Different DWPD. Equal daily writes.
3.84TB written per day
3.84TB written per day
Create a comparison sheet with capacity, DWPD, rating duration and TBW in separate columns. Ask the supplier to identify the exact specification behind each figure. If the numbers do not reconcile, resolve the difference before approving the order.
Product-family maxima also deserve attention. Micron’s 7600 specification lists different endurance classes for PRO and MAX models, with endurance tables by capacity. A family’s highest TBW figure should not be assigned to every drive carrying that family name. Micron’s 7600 technical specification illustrates why the exact model and capacity matter.
Build the requirement from observed writes
For an existing deployment, collect drive-level write counters over a representative period. Include the busiest recurring jobs, such as database maintenance or data ingestion, rather than extrapolating from a quiet afternoon. Record where the measurement comes from and its units so an application-level estimate is not silently compared with a different device-level counter.
Turn that evidence into a purchasing requirement: typical daily writes, exceptional peaks, expected growth and the planned service period. Ask the manufacturer whether its endurance rating applies to the intended workload. Keep performance requirements separate; meeting a write budget does not demonstrate that the drive will meet an application’s response-time target.
For example, a team planning a three-year deployment might evaluate its observed writes against several growth scenarios. That exercise is more useful than buying the highest DWPD label by default. Document the assumptions and review them when the application or retention policy changes.
For used SSDs, request evidence for each unit
A model’s original endurance specification is only one part of a used-drive assessment. Request the complete part number, firmware revision, serial-linked health report, recorded writes, test results and the seller’s warranty terms. Ask what the reported health fields mean for that model and which tool produced them.
Do not turn a remaining-life percentage into a promise of a fixed number of service years. Treat it as one input to a decision that also considers workload fit, condition, support and replacement arrangements. Sellers can make the comparison easier by supplying consistent reports instead of describing every unit with the same generic “healthy” label.
Buy an endurance specification that matches the workload—and retain the evidence that made the comparison possible.
Prepared November 10, 2026. Definitions follow Kingston; the product-family example follows Micron. The diagram is hypothetical arithmetic. Purchasing and inspection steps are Ocitech’s editorial recommendations, not drive-life predictions or independent benchmarks.