SSD Endurance Calculator: Host Writes to TBW

Worked examples

A 600 TBW drive reaches its rated host-write total after about 20.5 years at 80 GB/day. That answers the write-budget question. It says nothing about whether the drive will still work in year 20.

Default: 1 TB drive, 600 TBW, 80 host GB/day

• Inputs: Capacity = 1000 GB; rated TBW = 600; warranty = 5 years; daily host writes = 80 GB/day; WAF = 1.
• Result: Time to rated TBW = 20.5 yr | Rated host-write budget = 600 TBW | Host write rate = 0.080 DWPD (rated for 0.33 DWPD) | Host writes per year = 29.2 TB (4.9% of rating/yr) | Estimated NAND writes = 80.0 GB/day.

2 TB drive, 1,200 TBW, 150 host GB/day, assumed NAND WAF of 3

• Inputs: Capacity = 2000 GB; rated TBW = 1200; warranty = 5 years; daily host writes = 150 GB/day; WAF = 3.
• Result: Time to rated TBW = 21.9 yr | Rated host-write budget = 1200 TBW | Host write rate = 0.075 DWPD (rated for 0.33 DWPD) | Host writes per year = 54.8 TB (4.6% of rating/yr) | Estimated NAND writes = 450.0 GB/day.

Changing WAF from 1 to 3 triples only the NAND-write estimate. The host still writes 150 GB/day, so the rated host-TBW budget lasts the same amount of time at either setting. The assumed WAF in this example is an input, not a measured value for ZFS or any particular drive.

DWPD mode: 1.92 TB drive, 1 DWPD over five years, 150 host GB/day

• Inputs: Capacity = 1920 GB; rated DWPD = 1; warranty = 5 years; daily host writes = 150 GB/day; WAF = 2.
• Result: Time to rated TBW = 64.0 yr | Rated host-write budget = 3504 TBW | Host write rate = 0.078 DWPD (rated for 1.00 DWPD) | Host writes per year = 54.8 TB (1.6% of rating/yr) | Estimated NAND writes = 300.0 GB/day.

The five-year rating converts to 1 × 1.92 × 365 × 5 = 3,504 TBW. The 64-year result describes how slowly this example workload spends that budget. Warranty coverage still follows the drive’s terms.

How to use this calculator

Enter the drive’s capacity and its exact TBW rating. For a DWPD rating, enter the associated warranty period too. Then enter average daily host writes in decimal GB.

Use a measured write rate. Read the drive’s host-write counter at the start and end of a representative period, convert the difference to GB, and divide by elapsed days. Counter units vary by drive and interface; use the units reported by the drive’s utility or SMART documentation. I would use several representative days before choosing a higher-endurance drive for a VM or container host.

The six workload presets are illustrative inputs: 10, 30, 80, 150, 300 and 500 GB/day. A workload name does not measure your writes. Replace the preset with your own average.

TBW and DWPD use the same host-write budget

The conversion is:

TBW = DWPD × capacity (TB) × 365 × warranty years

A 1 TB drive rated at 0.3 DWPD over five years therefore has a 547.5 TBW budget, displayed as 548 TBW. The calculation keeps the unrounded value.

Samsung defines both ratings in terms of host writes in its SSD SMART attributes whitepaper, page 3. The 600 TBW default also matches the Samsung 990 PRO 1 TB specification.

NAND writes are a separate estimate

NAND WAF is the ratio of internal flash writes to host writes. At 150 host GB/day and WAF 3, estimated NAND writes are 450 GB/day. This output cannot determine physical wear without drive-specific endurance and wear information.

Use a measured NAND-to-host ratio when the drive exposes the required counters. Samsung’s SMART whitepaper, pages 4–5 describes that measurement for the drives it covers. Leave WAF at 1 if you only need the rated host-write budget; it has no effect on that result. Filesystem and application writes that have already reached the SSD are included in its host-write counter.

Read the result alongside drive health

These years start at zero accumulated host writes and assume a constant daily rate. They do not model prior use, data retention, electrical failure or changes in workload. Western Digital separates endurance from drive reliability in its SSD endurance whitepaper, pages 4–5.

For video storage planning, the Frigate NVR storage calculator estimates recording volume; measure actual SSD host writes once the recorder is running. Protect the recordings and other data with the Proxmox Backup Server 3-2-1 guide.