I am having an OCD dilemma, bought a WD40EZRZ-00GXCB0 with serial WCC7K2HR9Fxx (2 last serial digits not included because of warranty) made on 27 FEB 2020

It’s new and I still don’t want to open it, because if there is a chance it’s SMR I can sell it if it’s new and I don’t want it.

So this SHOULD be CMR since its “EZRZ” and everybody knows that “EZRZ” are CMR and “EZAZ” are SMR in this instance:

But…what makes me suspicions are the following internet threads, there is a reddit post, where somebody claims the difference between two models of WD Blue which are “EZRZ”:

WD40EZRZ-00WN9B0 - Giant (C4E in serial number) - 8 heads, PMR

WD40EZRZ-00GXCB0 - APOLLO (С7K in serial number) 6 heads, SMR.

Of course this just might be a mistake, I tracked the original post and it came from Russian forum, so I was searching further and found this website too:


With the claim:

WD40EZRZ-00GXCB0 – APOLLO (С7K in serial number) 6 heads, SMR.
BUT on their list here, it is not present as SMR.

I have checked the HDD with serial on WD site and this is indeed Apollo with 64MB of cache and with 6 heads as mentioned on various internet threads, can we say that this is a CMR 100% if it has 64MB of cache and is there a chance that it might be SMR because of the above threads I have posted?

Anyway, I would appreciate if somebody has the same HDD or want to make a philosophical debate out of this case or somebody with extreme knowledge who can shed some light on this dark and tough issue :)


This series consolidated with the older green series some time ago now

I have all the important details by model sorted by capacity

It would be great if somebody could give opinion regarding this topic is the mentioned HDD CMR or SMR, thanks.

OK to sum up, we have 2 “EZRZ” models of WD Blue in 4TB (“EZAZ” is of course SMR)

WD40EZRZ-00WN9B0 - Giant (C4E in serial number) - 8 heads, PMR (CMR)

WD40EZRZ-00GXCB0 - APOLLO (С7K in serial number) 6 heads, SMR or CMR?

Confusion is based on some internet posts where claims have been made that the second APOLLO model is SMR, because it has less heads (6) which means it has less platters too and it might use SMR because of that (density), but it has 64mb of cache too which would make it CMR since usually SMR HDDs have more cache, which is 256mb from WD.

I have contacted WD asking for confirmation too, really hoping they will respond.

Did WD reply?

1 Like

I’d like to know to, @Zer0lll. :sweat_smile:
I contacted them mysel today.

Hi guys, WD responded and confirmed that the HDD is CMR, to clear any confusion. Have a great day!

I was about to share the same news. I got a reply today.

I also have a My Book 4TB purchased in 2019. The drive is a Blue WD40EZRZ-00GXCB0 and upon researching, I’ve determined that it’s a CMR drive. That said, I understand that these days, most drives under 8TB are SMR.

How to CHECK if a disk is SMR or CMR: 4TB WD ELEMENTS with WD40EDAZ inside! SMR! Avoid! - #5 by marcolopes

If anyone needs to know WHAT INTERNAL DRIVE MODEL they have in their WD EXTERNAL ENCLOSURES, install https://crystalmark.info/en/software/crystaldiskinfo and COPY PAST the info to the clipboard! (EDIT → COPY or CTRL-C). Paste it to a text editor, and voila!!!

Then, compare the model against one of the HD DATABASES available

And check if they have SMR tech or not!

The [WD Blue 4TB hard drive](https://www.m4l.com/blog/enhance-your-storage-capacity-with-wd40ezrz-wd-blue-4tb-hard-drive/) is available in both SMR (Shingled Magnetic Recording) and CMR (Conventional Magnetic Recording) technologies. SMR drives are known for their higher storage density, which can result in cost-effective higher capacity drives. However, they may have limitations in certain write-intensive workloads due to their unique data recording method. CMR drives, on the other hand, are more traditional.