Western Digital has been receiving a storm of bad press—and even lawsuits—concerning their attempt to sneak SMR disk technology into their "Red" line of NAS disks.

To get a better handle on the situation, Ars purchased a Western Digital 4TB Red EFAX model SMR drive and put it to the test ourselves?

But when Servethehome used it to replace a disk in a degraded RAIDz1 vdev, it required more than nine days to complete the operation—when all competing NAS drives performed the same task in around sixteen hours.

This has rightfully raised questions as to what Western Digital was thinking when it tried to use SMR technology in NAS drives at all, let alone trying to sneak it into the market.

When we created the RAID6 array, we used the argument -b none, to keep it from attempting to perform a bitmap scan to do faster rebuilds when using a disk that had previously been in the array.

After formatting the new eight disk, 19TiB array, we dumped 14TiB of data onto it in fourteen subdirectories, each containing 1,024 1GiB files filled with pseudo-random data.

First, we fed the entire 4TB Red to the degraded array as a replacement for the missing, partitioned Ironwolf.

This gave us our two test cases—a factory-new Red SMR disk being rebuilt into an array, and a used Red SMR disk with a lot of data on it already being rebuilt into an array.

We weren't surprised that the SMR disk performed adequately in the first test—consumer ire aside, it seemed unlikely Western Digital had sent these disks out the door with no testing whatsoever.

We were more surprised that it performed the same way in a used condition as it had when new—the drive's firmware was able to shuffle data around well enough that it didn't take a single additional minute to rebuild from a "used" condition as it had when new.