Western Digital WD Purple: the whole line compared

What these specifications actually mean

A drive family is a promise about consistency: the maker is telling you that every model in the line is built for the same duty, so you can pick on capacity and expect the rest to follow. That promise is worth checking rather than assuming, which is what this table is for.

Warranty terms are not uniform across this line, running 3 to 9 years. That usually marks a split between capacity tiers, and it is worth checking which side the model you want falls on.

Every model here uses conventional recording, which is what makes the line safe for arrays end to end: a rebuild reads and writes the whole drive, and shingled recording is what turns that from hours into days.

Spindle speeds are not consistently stated.

What the family name cannot tell you is how any individual model actually fails in service. Reliability is a property of a model and its production run rather than of a brand or a line, which is why our measured failure rates are organised by model number. A family with a good reputation still ships models with poor rates.

What it suits, and what it does not

Choosing within this line: pick on capacity first, then confirm that the specific model carries the workload rating and recording technology you need. The table above makes the exceptions visible, and the exceptions are the whole reason to read it.

Choosing between lines: compare at a fixed capacity rather than in the abstract, because that is the decision you are actually making. Our capacity pages do exactly that, for example 4 TB.

Mixing models within an array: workable when capacity, recording technology and rotational speed match. Mixing a shingled drive into a conventional array is the case that bites, because the rebuild runs at the speed of the slowest member.

Buying the whole array at once: consider deliberately splitting across two production runs or two families. Drives bought together frequently come from one batch, and batch-correlated failures are exactly the scenario redundancy handles worst.

What to do with this

1. Shortlist by capacity, then check this table for the exceptions within the line.
2. Confirm recording technology on the exact model with our decoder before buying for an array.
3. Check the measured failure rate by model on our AFR table, reading drive-days before the rate.
4. Compare this line against others at your chosen capacity on the relevant price per TB page.
5. Work out real cost with the cost per TB calculator, including usable capacity after formatting.
6. Split a new array across two batches or families where you can, to avoid correlated failures.