PMR and SMR question

Recently, on a Synology device, to extend SHR storage i bought 2 x WD WD60EFAX.
Old pool was 4 x WD30EFRX and new pool is 2 x WD30EFRX + 2 x WD60EFAX

After some experienced issue around performance, i discover that WD60EFAX use a PMR technlogy as mentioned only on the Synology Products Compatibility List with this recommendation:

  • Due to the characteristics of SMR, this SMR drive might have longer response time than a PMR drive. It is highly recommended not to mix SMR and PMR drives in one RAID type. You can refer to this FAQ for more information.

So actually, i need to replace this new 2 x disks WD60EFAX because my SHR group is not right and i need to buy 2 others disks PMR and not SMR and WD provide no information about that.

My question is very simple: Actually, what RED models are or not PMR ?

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Although not an authoritative source, this article quotes WD as saying 2TB-6TB Reds use SMR, but higher capacity Reds use CMR (PMR).


For what it’s worth, I just contacted WD support. I asked them if my four 6TB WD60EFAX-68SHWNO drives are SMR, and if they were certified to function well when used in a ZFS filesystem doing a resilvering operation. WD Support gave me the answer:

  1. WD60EFAX models do not use SMR. The older WD60EFRX models do use SMR.
  2. Yes, WD60EFAX models are certified to be used in ZFS. (They did not answer specifically about performing well during resilvering.)
  3. No, there is no public WD document presently which clearly answers this question of SMR, and fitness for ZFS use.

This is different information than appears in other forums. Unfortunately, I don’t entirely believe it. I sure wish WD would make a clear statement on the matter.

Background on “ZFS resilvering”: ZFS is a kind of filesystem which uses multiple disks and redundancy to achieve high reliability. When one disk fails, (if you have set things up right), you lose no data, because of the redundancy. When you plug in a new drive, “resilvering” is the ZFS file system reconstructing the old disk’s contents on the new disk using the redundant information. Unlike many home NAS operations, resilvering makes many write operations to different parts of the disk, and this is a usage pattern that SMR performs poorly on.


Thanks all!!
It is a major point for us, WD RED customer as NAS and some other technology storage.

Waiting an official statement from WD about PMR and SMR features on each disk family/models and provide some clarification about Synology warning.

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WD EFAX drives 2-6TB are definitely using DMSMR

I consider this lack of disclosure and the fact that WD has been officially peddling these drives as CMR for almost a year a blatant lie and capital breach of trust.
I feel cheated for having bought those drives certain to having bought CMR drives in good faith, and now being stuck with inferior performance SMR drives ( my setup cares about the rewrite performance …)
I agree that in many use cases consumers wouldn’t feel the difference, nor be negatively impacted in any way.
Is WD planning on fessing up in a more public fashion and compensating buyers who feel cheated and who actually care about the drive performance? After all those drives are labelled “NAS” for a reason …

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In fact, due to my configuration (the original disks are PMR on a SHR / RAID5), I was forced to quickly replace 2 x 6 TB WD RED by 2 x 8 TB WD RED. The additional extra cost not expected by this joke is 70 € per disk (I took the cheaper box version than the bulk version) . So, yes i have 4 TB as extra storage but as a SHR group, my user storage is just an extra of 2 TB.
Now, i hope that Amazon accept a refund. If not, i sell 2 x WD 60 EFAX to WD as real cost.

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Would WD accept to buy back recent drives? Mine are 3 months old … I suppose I’m stuck with them.
And what’s to say my “use case is within DM SMR’s capability”?
I especially bought these drives because they were advertised as CMR everywhere and I explicitly wanted to avoid all the known SMR drawbacks. Who’s WD to argue that my “use case” would not warrant such a choice?

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60EFAX are SMR!!! WD publishes complete list of SMR drives following user backlash | TechSpot


I have DOZENS of them, mostly external! STUPID of me!!!

I will choose CAREFULLY from now on, buy INTERNAL drives, and use my own ENCLOSURES! No more ADVANCED FORMAT ■■■■ nor SMR.


Oh, I agree. In my April 16 post, I reported what WD support told me, and I said, “I don’t entirely believe it”. WD’s subsequent public statements show that this support person was mistaken.

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Someone said this is part of a RACE for BIGGER capacities. It can be… BUT, before that happens, WD is probably using the most demanding customers / environments to TEST SMR tech so they can DEPLOY them in the bigger capacity DRIVES: 8, 10, 12, 14TB and beyond (do not currently exist). I say this because, WD has the same “infected SMR drives” using the well known PMR tech!

Why is that? Why keep SMR and PMR drives with the SAME capacity in the same line and HIDING this info from customers? So they can target “specific” markets with the SMR drives? It seems like a marketing TEST!!! How BIG is it?

Note that currently, the MAX capacity drive using SMR is the 6TB WD60EFAX, with 3 platters / 6 heads… So… is that it?? Is WD USING RAID / more demanding users as “guinea pigs” to test SMR and then move on and use SMR on +14TB drives??? I’m thinking YES!! And this is VERY BAD NEWS. I don’t want a mechanical disk that overlaps tracks and has to write adjacent tracks just to write a specific track!!!

Customers MUST be informed of this new tech, even those using EXTERNAL SINGLE DRIVES ENCLOSURES!!! I have many WD external drives, and i DON’T WANT any drive with SMR!!! Period!

Gladly, i checked my WD ELEMENTS drives, a NONE of the internal drives is PLAGUED by SMR! (BTW, if you ask WD how to know the DRIVE MODEL inside an external WD enclosure, they will tell you it’s impossible!!! WTF is that??? WD technicians don’t have a way to query the drive and ask for the model number?? Well, i got new for you: crystaldiskinfo CAN!!! How about that? Stupid WD support… )

So, if anyone needs to know WHAT INTERNAL DRIVE MODEL they have in their WD EXTERNAL ENCLOSURES, install CrystalDiskInfo - Crystal Dew World [en] and COPY PAST the info to the clipboard! (EDIT → COPY or CTRL-C). Paste it to a text editor, and voila!!!

(1) WDC WD20EARX-00PASB0 : 2000,3 GB [1/0/0, sa1] - wd
(2) WDC WD40EFRX-68N32N0 : 4000,7 GB [2/0/0, sa1] - wd
(3) WDC WD1600BEVS-22UST0 : 160,0 GB [3/0/0, sa1] - wd

Compare this with the “INFECTED” SMR drive list, and you’re good to go!!!

there isn’t just black or white point of view. You need read more about SMR, because tests provided by STH (your link provided) defined an useful target if the SMR disk drive target usage. Just to be sure copy of the 125GB single file is far away from standard reality of NASes operation (as was used in the mentioned test).
So, I’m also not happy from the “hidden” strategy of HDD vendors (all 3 vendors) about SMR till this public pressure. But you need to understand that SMR is also useful and you have a choice.
More you can read in our independent
Part No. 1

Part No. 2
or you can enjoy the ProGrade level forum based on real/practice evaluations too far from “laboratory” test attitude mentioned above.

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I understand that SMR is also useful but I do not have a choice. My drives were purchased for a NAS in mid 2017 and I need to know what sort of drives they were, then, not now.

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I use JBOD on my box and I have been fortunate that shingled disks have not been problematic. NAS boxes should used the WD gold disks which are faster and not shingled.

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I have two WD Red 3TB HDDs which are a few years old - bought them because they were advertised as designed for NAS.

They were in Storage Spaces mirrors, which just stopped working one day. One of the drives is fine, another shows write speed of just a few MB/s with normal reads (sounds like SMR). They have identical product number and firmware (WDC WD30EFRX-68EUZN0 82.00A82). The only difference is a serial number - one (bad one) starts with WD-WCC4N and another - with WD-WMC4N). Both are out of warranty.

I do feel like WD cheated on me - drivers marked the same turned out to be different. And selling SMR as a NAS drive without even discussing it. What a sick person can have such idea?

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SMR disks are drive managed and are transparent to an operating system

Reliability is a totally different issue