Skip to content 
TBW (Terabytes Written)
Flash memory wears out when written to. How much an SSD can withstand according to the manufacturer is stated in the data sheet as the TBW value. That is as useful for planning in operation as it is for the question of whether a decommissioned SSD still has a second life ahead of it.
In brief
TBW (Terabytes Written) is the amount of data in terabytes that a manufacturer guarantees an SSD can have written within the warranty period. The value describes the expected write endurance, because flash memory cells can withstand only a limited number of write cycles. In IT decommissioning, comparing TBW with the amount of data already written shows how heavily an SSD has been used and whether it is suitable for reuse.
What does TBW mean for an SSD?
A SSD stores data in flash cells. Each cell can go through only a limited number of erase and write operations before it becomes unreliable. The controller therefore distributes the write load evenly across all cells. This method is called Wear leveling.
The TBW value sums up endurance in a single number. If a manufacturer states, say, 600 TBW, it guarantees that 600 terabytes can be written within the warranty period. In many warranty terms, the warranty ends as soon as the warranty period has expired or the TBW value has been reached – whichever occurs first. An SSD does not automatically fail after reaching the TBW value. From that point on, however, the manufacturer gives no further assurance.
TBW, DWPD, and lifespan
For server SSDs, endurance is often stated in DWPD (Drive Writes Per Day). The value says how often the entire capacity may be written per day over the warranty period. Both figures can be converted into one another.
| Key figure | Significance | Conversion |
|---|---|---|
| TBW | Total guaranteed write volume in terabytes | TBW ≈ DWPD × capacity in TB × 365 × warranty years |
| DWPD | Full drive writes per day | DWPD ≈ TBW ÷ (capacity in TB × 365 × warranty years) |
| Amount of data written | Actually written so far | Can be read out via the S.M.A.R.T. values |
Simplified calculation example: an SSD with 1 TB capacity, 0.3 DWPD, and five years of warranty comes to roughly 0.3 × 1 × 365 × 5 ≈ 548 TBW.
How much has already been written is stored by the SSD itself. On NVMe SSDs the value is called "Data Units Written"; one unit corresponds to 512,000 bytes. Many NVMe SSDs also report under "Percentage Used" how much of the estimated lifespan has been consumed. On SATA SSDs the names depend on the manufacturer. More on this under S.M.A.R.T. values.
TBW when decommissioning
In office notebooks, SSDs are usually written to well below their TBW value. Many decommissioned SSDs therefore still have a large part of their endurance left and can be reused after they have been securely erased. The situation is different for SSDs from servers, databases, or video editing that have written a great deal.
For the decision between reuse and destruction, the measured condition therefore counts. Important: endurance says nothing about data security. Even a heavily worn SSD can contain readable data. Which erasure methods are suitable for SSDs is described in the guide Securely erasing hard drives and SSDs.
Key takeaway: TBW is a warranty commitment, not an expiration date. The measured condition shows whether an SSD can be reused.
SSD testing at Second IT
Second IT erases SSDs software-based with Blancco and issues a digitally signed erasure certificate for every device. In refurbishment, devices are checked in comprehensive functional tests and documented in a test report. Data carriers that cannot be erased are destroyed in-house in accordance with DIN 66399. More on the certified data deletion.
Frequently asked questions about TBW
What happens when an SSD reaches its TBW value?
Usually it continues to work at first. From this point on, however, the manufacturer gives no warranty, and the probability of failure rises. For important data, such an SSD should be replaced.
How do I find out how much has been written to my SSD?
Read it out via the S.M.A.R.T. values, the manufacturers' diagnostic tools, or general programs. On NVMe SSDs the value is found under "Data Units Written".
How long does an SSD last?
That depends mainly on the write load. With typical office use, many SSDs do not reach their TBW value within the service life of the device. A blanket statement in years is therefore not possible.
What is the difference between TBW and DWPD?
TBW is the total guaranteed write volume in terabytes. DWPD states how often the entire capacity may be written per day over the warranty period. DWPD is common for server SSDs. Both figures can be converted into one another.
Can I reuse a decommissioned SSD?
Often yes. In office notebooks, SSDs are usually written to well below their TBW value and still have a lot of endurance. After secure erasure, reuse is possible. For SSDs from servers with a high write load, the measured condition counts.
Erase, test, and reuse SSDs – with documentation.
Send us your device list. You will receive your offer in 48 hours on average.