PSA: Beware of HDD manufacturers submarining SMR technology in HDD's without any public mention

Recently there have been several reports of SNOs running into massive CPU wait issues. It seems the common thread has been the use of HDD’s in which manufacturers have quietly started using SMR technology.

Because of these overlapping tracks, when data is written to the disk, the drive has to rewrite several additional tracks. This obviously leads to much slower writes. These HDD’s usually deal with that using large caches and rewriting the shingles tracks during quiet times. However recent storj traffic has been constant and fairly heavy. It seems this is causing systems using these SMR based drives to topple.

Unfortunately the manufacturers are incredibly cagey about this whole thing. No mention of the use of SMR on spec sheets or any official communication. Luckily the website has done some research and written articles about the three major HDD manufacturers and their use of SMR.

You’ll find those here:

I guess for now we all need to be very careful and play a little detective before buying HDD’s. And hopefully public pressure will make them change their minds about hiding this vitally important difference between SMR and PMR drives.

Edit: Some manufacturers have now published a list of HDD’s currently using SMR. These lists are likely outdated soon, but it’s a start. They’re promising to be more transparent about the use of the tech as well. Here are links and models.

Known SMR HDD’s

Western Digital (current as of 2020-04-22)

WD Red 3.5”

  • 2TB WD20EFAX
  • 3TB WD30EFAX
  • 4TB WD40EFAX
  • 6TB WD60EFAX

WD Blue 3.5”

  • 2TB WD20EZAZ
  • 6TB WD60EZAZ

WD Blue 2.5”

  • 1TB WD10SPZX
  • 2TB WD20SPZX

WD Black 2.5”

  • 1TB WD10SPSX

Toshiba (current as of 2020-04-28)

Desktop PC & Surveillance Hard Drive range (P300 / DT02 / DT02-V)

  • P300 6TB
  • P300 4TB
  • DT02 6TB
  • DT02 4TB
  • DT02-V 6TB
  • DT02-V 4TB

Laptop PC Hard Drive (L200 / MQ04)

  • L200 2TB
  • L200 1TB
  • MQ04 2TB
  • MQ04 1TB

Seagate (current as of 2020-07-27)

Desktop 3.5"

  • BarraCuda 2TB
  • BarraCuda 3TB
  • BarraCuda 4TB
  • BarraCuda 5TB
  • BarraCuda 6TB
  • BarraCuda 8TB
  • Archive 8TB
  • SkyHawk Lite/Mini 1TB
  • SkyHawk Lite/Mini 2TB
  • Exos 5E8

Laptop 2.5"

  • BarraCuda 500GB
  • BarraCuda 1TB
  • BarraCuda 2TB
  • BarraCuda 3TB
  • BarraCuda 4TB
  • BarraCuda 5TB
  • FireCuda 1TB
  • FireCuda 2TB
  • SkyHawk Lite/Mini 1TB
  • SkyHawk Lite/Mini 2TB

List provided by Seagate is unfortunately missing model numbers. It also seems to be limited to consumer drives, Exos is missing.
I added that Exos X series are SMR free, but Exos E series use SMR.


Has someone researched this so it can be posted here ?

I’m using WD Red 4TB, 8TB and Seagate Ironwolf 8TB and really want to know.

Use ls /dev/disk/by-id and check if the disk model number is affected in the articles linked above. Fortunately, my disks are EFRX, PURZ and EMAZ so I don’t seem to be affected. I’ve done several successful rebuilds as well, confirming this.

I linked the relevant articles in my post. WD seems to have used it in some NAS disks, but you can tell from the makeup of their model numbers. Which hopefully also applies to some future models.
For seagate it applies to a desktop model and some barracuda models. Seagate Exos E series also uses SMR.
Toshiba used it in desktop drives as well.

The article lists some model numbers, but I don’t know if those lists are complete. And I doubt they’ll update the articles when new HDD’s are released. Luckily some googling can help out. But I’m intentionally not listing specific models because an incomplete list could be worse than no list at all. Just make sure yourself that any model you want to buy doesn’t use SMR.

Currently, Western Digital’s WD Red 2TB-6TB drives are device-managed SMR (DMSMR). WD Red 8TB-14TB drives are CMR-based.

That’s interesting. Bigger drives are normal, but smaller ones are SMR, kind-of opposite of what I would expect. I guess I won’t be buying Red drives anymore.

Yes it seems to be a cost saving measure more than an actual density problem. I believe all manufacturers have HDD’s up to 16TB without SMR. So it’s not needed to get to such sizes.
What makes it worse is that the SMR versions of these drives aren’t even cheaper for the consumer buying them. It seems they’re pocketing the difference instead.


Looks like some SMR drives can make use of TRIM to help keep the drive ready for writing. TRIM Command Support for WD External Drives I wonder if the OS will automatically use trim on a non SSD drive though?

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I read the Western Digital link but I found it a little bit unclear. The WD red I have is EFRX so I’m probably ok as ‘Derkades’ say.

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I believe this information is important enough that it should go into documentation, probably to


EFRX are old drives, well, at least mine are old, so they should be normal.

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I have a WD 12TB usb drive and you can actually hear it when it does its SMR housekeeping
For a few seconds it makes a noise, several times a day.
No mention of SMR in the box or description at all.

It is the same noise that the new WD reds make.

It might be worth linking to the Synology’s compatibility list:

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Its funny were talking about this and gamernexus is talking about it on youtube now…

It’s been blowing up over the past few days since posted their articles a few large publications posted it and got the snowball running. Today one of my podcasts discussed it as well.

So, it’s good to see it getting some exposure as that’s the only way manufacturers might change their mind around the secrecy. And it will definitely cause reviewers to always include this info.

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Yeah I agree its screwed up and now I have 3 new drives that are all SMR…

Damn it :frowning: Its exactly the one I bought…The WD Red NAS DRIVE…crap!

Return it if you bought it’s less than 2 weeks ago online.

Not possible as I migrated my oldest node to this HDD.

While testing the compression radio I noticed that two drives of my storj array are much slower than the rest. It turns out that they are SMR (ST4000DM004), I have bought them a while ago and used them on Storj v2. So this has been happening for a while now.

At the time I bought the drives, I was looking for cheap drives, but decided to buy Barracuda (desktop) on the assumption that they would not be SMR (Archive drives were a bit cheaper).

However, it turns out that in a raidz2 array with 4 normal drives and two SMRs, L2ARC and ZIL these ones behave acceptably, at least with the current node traffic. I probably would not gain much by replacing them with two fast drives, well, at least while these ones still work. However, if I need to expand the array I’m going to buy normal drives.

what is your “current node traffic” ?
I created a node 3 weeks ago, with a raspberry and an ST4000DM004, a few days ago the node crashed, it was receiving mode than 200GB / day for 3 days, and I’m almost sure the source of the problem is the drive not responding while “reorganizing” the data.
I found a documentation about the ST4000DM004 (and other variants from 2 to 8 GB) which said “Rated workload | Average annualized workload rating: <55 TB/year. …”
55TB / 365 = 0.150TB = 150GB/day
I guess those disks can be used if the traffic is not too high, but exceeding some limit they do not respond for too long and the system disconnect them :s