Enterprise SSD quotes often come down to endurance, not headline speed. TBW and DWPD are the two numbers buyers compare, and they are easy to misread. This guide explains what they mean, how they are measured, and what to ask before you compare prices.
1. TBW: total bytes written
TBW (terabytes written) is the total volume of data a drive is rated to write over its warranted life. It is a endurance budget, not a guarantee that the drive dies exactly at that number: the rating is tied to the warranty period and the workload model the vendor used.
A 3.84TB read-intensive drive rated at roughly 1 drive-write-per-day (DWPD) over five years works out to several thousand TBW. A mixed-use drive of the same capacity is often rated two to three times higher — and costs more per drive because it uses higher-endurance NAND and over-provisioning.
2. DWPD: drive writes per day
DWPD expresses the same endurance budget in a more intuitive unit: how many times the drive’s full capacity can be written every day for the warranty period.
- Read-intensive (~1 DWPD): boot volumes, read-heavy databases, web serving, virtualisation hosts with low write amplification.
- Mixed-use (~3 DWPD): write-heavy databases, logging, analytics and virtualisation with sustained write load.
- Write-intensive (~10 DWPD): caching tiers, journaling and specialised write-heavy workloads.
DWPD is derived from TBW, capacity and warranty years, so the same TBW number means different things at different capacities. Always check the capacity and warranty period attached to the rating.
3. What actually drives wear
Host writes are only part of the story. Write amplification — the extra NAND writes caused by garbage collection, over-provisioning and workload patterns — can multiply the effective wear several times. Random small writes are far harsher than sequential writes. That is why the workload class matters more than the raw TBW figure when sizing a fleet.
4. SMART wear indicators to request
For new drives, endurance is a specification. For refurbished or new-pull SSDs, it is a measurement. Ask for the SMART attributes that show remaining life:
- Percentage used — the vendor’s estimate of endurance consumed.
- Total data written (host writes and NAND writes where available).
- Power-on hours and power cycle count.
- Media errors / uncorrectable errors.
Per-serial evidence is the only useful form: a batch-level claim tells you nothing about the drive you will receive. Our testing & QC process records these values for used stock.
5. Procurement checklist
| Check | What to confirm |
|---|---|
| Workload class | Read-intensive / mixed-use / write-intensive, matched to writes per day |
| Endurance rating | TBW and DWPD, with capacity and warranty period stated |
| Interface | SATA, SAS or NVMe — matched to the backplane, not assumed |
| Form factor | 2.5-inch SATA/SAS or U.2/U.3 NVMe |
| Condition | New, new-pull or refurbished, stated per line |
| Wear evidence | SMART percentage used + total data written per serial |
6. How we quote
Send the model or part number, the workload (or expected writes per day), quantity and destination country. If you are unsure between read-intensive and mixed-use, send the workload instead of a model and we will propose matching options with the endurance class stated.
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