WD11PURZ: full specifications and current price

What these specifications actually mean

The two specifications that decide whether this drive belongs in an array are the recording technology and the rated workload, and they are worth taking in that order. The WD11PURZ uses conventional recording, which means tracks do not overlap and a rewrite costs no more than a first write. That is what makes it safe for RAID and ZFS: a rebuild reads and writes the whole drive, and a shingled drive can slow by an order of magnitude doing it.

This datasheet does not state a workload rating, which is common on consumer lines. Treat the absence as a sign the drive is not sold for continuous multi-drive duty rather than as permission to ignore the question.

The rated MTBF of 300,000 hours implies an annualized failure rate of about 2.92%, which is the same number expressed in units you can use. It does not mean the drive lasts 34 years. It is a population statistic measured during the useful-life period, before wear-out begins, and it says nothing about your specific unit. Our MTBF to AFR calculator does that conversion and explains why the headline number reads as more reassuring than it is. Backblaze does not run this model in sufficient numbers to publish a measured rate, so the rating is the only figure available.

The 64 MB cache matters less than its size suggests. It buffers bursts and helps with reordering, but once a sustained transfer exceeds it the drive runs at platter speed. Treat it as a tiebreaker between otherwise equal drives rather than a headline feature.

What it suits, and what it does not

In a NAS or RAID array: suitable. Conventional recording and a workload rating are the two things an array actually needs from a drive, and this has them.

As a single desktop or backup drive: fine in almost every case. The constraints that rule drives out of arrays, mostly rebuild behaviour, do not apply when nothing is rebuilding. A shingled drive used as a backup target that is written once and read occasionally is working exactly where its density advantage is free.

In a surveillance recorder: the workload rating is the deciding figure, because a camera array writes continuously rather than in bursts. Without a stated rating, prefer a drive sold specifically for surveillance.

What the specifications cannot tell you is how this drive behaves in your enclosure. Vibration from neighbouring drives, airflow and power quality do more damage than the difference between two well-rated models, and none of it appears on a datasheet. Our measured failure rates come closer, because they are observations rather than ratings.

What to do with this

1. Confirm the recording technology before buying for an array. Our model number decoder reads it from the part number and says plainly when it cannot.
2. Check the measured failure rate for this model, not the brand, on our AFR table, and read the drive-days column before trusting any rate.
3. Compare against the rest of the line on our WD Purple page, which covers 5 other models.
4. Compare against every other drive at this size on our 1 TB page, which ranks by price per terabyte.
5. Work out the real cost with our cost per TB calculator, which also shows the usable capacity your operating system will report.
6. Register the warranty as soon as it arrives. It runs from manufacture, not purchase, unless you file proof: our warranty check covers each maker's process.