16TB Showdown – WD HC550 vs Seagate EXOS 16 vs Toshiba MG08

Hard Drive Interals

The three cheapest SATA 16TB drives available at the moment (March 2021) are all around $350: the Seagate EXOS 16, the WD Ultrastar DC HC550 and the Toshiba MG08 Series. I planned on using two of each in my home NAS, until a shocking discovery while doing a quick benchmark on them! To spoil the suspense, the Toshiba was either defective or was designed with different workloads in mind.

A quick note: these were all purchased out of pocket for my own setup. I do not have any sponsors, nor any advertising on my website. These results are purely my own findings. I simply wanted to share to those who may be interested.

The Contenders

As you may have guessed, these 16TB drives have a lot in similar. Each drive is helium filled, 7200rpm and SATA III (6.0Gb/s). The three of them also offer 2.5M hours of Mean Time Between Failures and max 550TB/yr workload. There are a few subtitle differences though.

WD Ultrastar
DC HC550
MG08 Series
Block512e / 4Kn512e / 4Kn512e OR 4Kn

They also sport a few physical design differences. The WD seems to be “upside down” compared to the others, and the standard middle side screw hole did not line up in my case.

For those who are design conscious, the EXOS is the only one offering a splash of color, and none of them offer RGB lights. Though if you are looking for RGB lights on a HDD, you might need a mental recalibration via wrench to the side of the head. HDDs are like construction workers, they work all day and are only noticed when they are slowing things down.

The Test Machine

This system was not designed to pump out the best benchmark performance. This is a real world NAS I will be using for my house. That said, it may not eek out the most performance on these drives, but it does give us a standard base for comparison.

  • Operating System: TrueNAS SCALE 21.02 Alpha
  • CPU: Ryzen 5 5900x 12-core 3.7GHz
  • Motherboard: ASRock X570 PHANTOM GAMING 4
  • Memory: NEMIX RAM 64GB DDR4-3200 P 2Rx8 ECC Unbuffered Memory
  • PSU: CORSAIR RM Series RM750
  • HBA: Dell H310 LSI IT mode 9211-8i

The hard drives were all connected to the HBA card and tested one at a time. They were setup into single ZFS pools using the TrueNAS UI with record sizes set to 512K.

All three drives are the exact same size (perfect for a NAS setup) and using the same 512e block size.

14.55 TiB, 16000900661248 bytes, 31251759104 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Benchmark Results

Read Speeds

These were gathered by running hdparm -tT twice on each drive and taking the better of the two (they were extremely similar and didn’t seem to merit more tests).

They were all so close we really need to “zoom in” on the differences.

That’s a bit better. However it exaggerates the real world difference because the lack of scale, so keep that in mind (never trust a graph that doesn’t start at zero!) Out of the three, Seagate EXOS 16 looks to be the sweet spot for cached and buffered read speeds. The other two both put in great numbers for spinning platter disks, and may want to stick to the WD if you will be working with frequently cached data.

Write Speeds

Each Benchmark for the write speeds were done using the dd command three times each to pump output from /dev/urandom to each drive. The tests will not encounter compression or caching done during the runs with this design. This means these numbers are for comparison to each other only and not max speed. Each drive was in a single ZFS vdev by itself with a record size of 512k.

Large blocks

The Seagate and WD perform nearly the same, well within margin of error of each other. The Toshiba is noticeably slower, but still within expected disk drive speeds.

dd if=/dev/urandom  of=/mnt/<dive>/tmp.file  bs=4096k  count=1000  oflag=dsync

Medium blocks

Here is where the Toshiba MG08 started to really worry me. Its write speed of medium 1M block sizes is half that of the others.

dd if=/dev/urandom  of=/mnt/<dive>/tmp.file  bs=1M  count=1000  oflag=dsync

Small blocks

Full on nosedive for the Toshiba, over four times slower than the other drives.

dd if=/dev/urandom  of=/mnt/<drive>/tmp.file  bs=4096  count=1000  oflag=dsync

After reviewing the data, I am convinced that the drive is either defective or is designed for a different type of workload than what is in my setup. I did reach out to other enthusiasts on the /r/homelab discord and nothing seemed to cause that dip due to methodology at least.


Both the WD Ultrastar HC550 and Seagate EXOS 16 seem to be good choices for a home NAS. Others seem to also have great performance with the Toshiba MG08, that I was not able to duplicate in this instance. I wish I had the capability to grab another Toshiba to see if this was just a defective drive or my setup, but I can’t just throw cash at it.

For now I am putting together a combo of WDs and Seagates into my NAS and calling it good. Hope you found this information useful!