NAS Compares Your WD Red NAS Hard Drives Might Be Using SMR – What You Need To Know

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NAS Compares Your WD Red NAS Hard Drives Might Be Using SMR – What You Need To Know

WD Red 2TB, 4TB and 4TB NAS Hard Drives Use SMR / DM-SMR

Over the last few days, a story has been circulating that revolves around WD Red NAS Hard Drives and their potential use of shingled magnetic recording (SMR) and a statement has been shared by the brand highlighting that this is indeed the case, namely, drive managed shingled magnetic recording (DM-SMR). Now, it turns out this is something that many platforms and solo users online had reached the conclusion of as early as July 2019 and when reaching out to WD, and was met with less than immediate responses. But now it appears that the WD Red 2TB, 4TB and 6TB Standard class NAS 3.5″ Hard Drives do indeed feature this method of platter utilization inside and it’s upset a few people indeed, but the details are not as black and white as some might think. So, what is SMR, Should you be concerned, What does this mean for bigger WD Red Capacities and How is WD responding to this? Let’s take a look at the news.

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jeyare

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So is it cheaper to make them SMR? I think I read that it is, but not sure. If so, are they passing any of the savings to the consumer?
it’s totally different technology for the disk platters and ...
then there is just one advantage: more storage space in same box (3.5” form factor), Vendors have perfect story telling for customers, that price of GB (or TB) is dropping down.
Then people can buy more disks. And more disks make more profit. And more profit means, that pension funds can make more profit for share purchased for better pensions of mutual funds holders. We need better pensions. Then we are responsible for SMR technology. Hm, time to break.
SRM is still less costly technology than new form factor for HDD, because physical boundaries of the 3.5” are achieved.
 
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but here's the additional kicker - the WD Red SMR vs WD Red CMR drives are priced the same. WD is making SMR cheaper but not making them cheaper to buy.
 
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I found this info from "some place" searching for info aboute this FU, if it´s unpropriate just delete it...


- The preferred marketroid term for "normal" drives is now "CMR" - Conventional Magnetic Recording. BE VERY CAREFUL TO USE IT WHEN ASKING QUESTIONS

- PMR stands for "Perpendicular Magnetic Recording" (the way the magnetic domains are packed on the platter, vs Longitudinal magnetic domains of yore)

- Shingling (SMR) is Shingled PMR. It's built on top of PMR

- TGMR is a head technology needed for PMR and is the same for SMR or CMR

- TDMR( Two Dimensional Magnetic Recording ) is a weaselly way of saying "zoned media" and the only reason you have zoned media is.... because it's SMR (you need the zones to be able to do rewrites)

- Helium does not imply CMR or SMR. You can get squeaky drives in both formats,- HOWEVER you can infer probable SMR for air-filled drives above 4TB/3.5" 2TB/2.5"



So:

- If you are told a drive is PMR, therefore not shingled.... BZZT: see above.

- If you are told a drive is TGMR technology, therefore not shingled, see above

- If you ask "is this drive SMR or PMR?", the correct answer is "yes"

(All mechanical drives on the market use PMR, whether CMR or SMR and regardless of speed. This is because all 3 makers use the same platters and heads - each made by only one manufacturer)

Some other points:

- Drives whose datasheets show them as being substantially lighter than their predecessors are likely to be SMR

- Drives with large cache (256MB+) are extremely likely to be SMR - they need it to work (there are data tiering functions in Drive Managed SMR drives (DM-SMR) akin to those found in TLC/QLC SSDs - but much MUCH slower....)

- Drives reporting "trim" functions _ARE_ SMR, even if they don't report zoned media (Reporting zoning is a ACS-4 function - whilst that was codified in 2016, many drives are still only ACS-3 which doesn't support this reporting function.... hmmmmm... I wonder why that might be? Nothing suspicious to see here citizen, move along!)

- HOWEVER - Not all SMR drives report trim functions and the only way to find out is to benchmark the things - (Seagate barracuda ST3000DM003 being a good example)



- PAY ATTENTION TO THE SUFFIXES, READ THE SPEC SHEETS.

- COMPARE WITH PAST MODELS

- a generational change (from 003 to 004, or from EFRX to EFAX) may well mean a change has been submarined into the channel. Check the drive mass. Losing a platter at the same size is a sure sign of it having happened.



Above all: Complain loudly to your local marketing regulators about this misleading behaviour. WD and SG KNOW we don't want SMR, which is why they're going out of their way to keep it off their datasheets (European and Chinese regulators should be especially receptive to fraudulent marketing and cartel behaviour complaints)

(+) see the IEEE article below. The only references to "Parallel Magnetic Recording" anywhere on the web are on review sites and it's 100% clear they're a result of an utterly clueless reviewer guessing what the initials meant, then that guess spreading meme-style amongst other cluess reviewers who apparently don't know how to read tech documents (ie: You can pretty much surmise that such reviews are paid-for, as anyone independent will be doing their homework - and murketers aren't going to be falling over themselves to correct such an error)

(there ARE reference to lab work for recording calibration and sync tracks in parallel, but what THAT means is that they're activating multiple heads at once instead of the normal sequential switching between individual heads. (Attempts at parallelising heads in-service have never worked well due to differing thermal expansion of platters due to slight temperature changes across the case internals))

EDIT: This IEEE article is worth reading. IEEE Xplore Full-Text PDF:
 

jeyare

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Last edited:
some basic description you can find also in this thread
I saw the long description from @Smile in Reddit. Then step by step to fact fullness :

1. from technology point of view we know PMR (perpendicular magnetic recording) as leading HDD technology from 2005. Reason = run for more Areal density measured in Gigabits per square inch = better utilization of the HDD form factor. Toshiba as first vendor prepared 133Gb/sq inch for PMR HDD, ... then race has been started.

2. CMR is also known as PMR till 2014, when was commercially implemented second derivate of PMR - called (SMR), from this time I have seen many times called just two technology CMR and SMR. Boot are PMR based from magnets orientation in platter point of view, but essentially different from rest of principles. Then both need different manufacture processes. Just to be sure.

3. main difference between CMR (PMR) and SMR (PMR), simplification:
- CMR is based on enough width (guard space) of highway lanes (disk capacity), then cars can securely drive with defined speed and direction, without additional complicated regulations. Reason why CMR can’t provide more highway lanes in closed environment (3.5” HDD form factor)
- whilst SMR is based on really shorter (tiny) highway lanes width, without the guarantee space for the car in single lane. What is risky, but achievable for really low traffic (low workload mentioned above). But in common traffic (when you have all lanes almost full) you need regulate all the cars separately in these lanes to achieve all the car in movement = reason of existence mentioned DMSMR. Then you have achieved model of more highway lanes, but really slow movement of the cars vs normal highway (CMR).
Back to disk technology terms - SMR must overwrite adjacent magnetic tracks and then rewrite them. Reason why they are so slow and why they need bigger cache for such operations. To be sure - SMR Areal density for first such produced HDD was 1Tb/sq. inch!
 

jeyare

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From this consideration point of view seems to be relation between number of platters and disk capacity and used technology:
- same capacity & more platters ... 99% for CMR (because less Areal density)
Search, check the important information, check the price, then buy.
 

jeyare

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as I wrote few weeks ago PMR is gone and HAMR technology will replace the PMR. First HDD is commercial available from Seagate.

Then it’s not necessary to write more about TDMR technology, because:
- yes it contains shingled recording, but with doubled heads, then this isn’t identical to PMR/SMR
- needs really fast speed controller (then usage in NAS with low end CPU is considerable), also for low end laptops
 

jeyare

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re Helium:
more suitable for more platters equipped HDD, because it’s need homogeneous environment = reason of Helium filled disk.
And more platters for same capacity = CMR
 

jeyare

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(All mechanical drives on the market use PMR, whether CMR or SMR and regardless of speed. This is because all 3 makers use the same platters and heads - each made by only one manufacturer)
I would like to correct this statement:
WD(incl. Hitachi), Seagate and Toshiba use similar platters and heads technology because they use same patented technology derivates: CMR or SRM for its production
 

jeyare

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Tomorrow I will prepare a blog post here with summary of the concern (and advantages) about SMR
 
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Again, a lot of technical stuff, but in reality what difference does it make to the end user?
 
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Chenks - in the end, you simply want to know that the hard drive you are using in your NAS is suited for that purpose.
 
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Chenks - in the end, you simply want to know that the hard drive you are using in your NAS is suited for that purpose.

that's a politicians answer.
i'm asking if there is any noticable performance issue between the two types.
 
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Last edited:
that's a politicians answer.
i'm asking if there is any noticable performance issue between the two types.
I think the answer is the classical “it depends”.

Depends on what you are doing with the NAS. I believe I read if it’s under a heavy writing load constantly, the cache buffer can’t keep up because of how SMR writes (sequentially which is slow compared to CMR) or something to that effect. The end result is slower performance. That‘s what I understood.
 
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I have 3 X 4TB WD Reds. 2 from 2016 and 1 late 2019. Turned out they are all CMR (according to WD).
All are WD40EFRX.

Check what you have via DSM. No need to pull out the disks.
Storage Manager > HDD/SSD
 

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