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A2116 / 2019 / 3.6 GHz quad-core i3, 3.0 GHz 6-core i5, or 3.2 GHz 6-core i7 processor. Released March 19, 2019.

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Deeper insight into blade SSD’s

I know this is an old thread, but I would like to hear more from Dan on the Limits, and the "Sizable Chance" he speaks of. What EXACTLY have you seen as issues? Mainly the "Garbage collection" and "Protocols" that Apple runs that would not be supported?; Over-filling any SSD, under any circumstances [including phones] is a source of early failure [I like to leave mine around 1/3 empty].

SO hard to mix and match configurations to get the MOST, without breaking something, or "over-buying and not getting the benefit. I too have a 2019 imac-i9 and am currently booting from an external PCIe 3.0-NVMe-M2-4TB. IF I can't achieve anywhere near the speeds I am seeing going internal, I won't waste my time/$. It APPEARS that the 2019 iMAC does support the PCIE 3.0 NVMe-NOT M2? [IF I am reading correctly]; and not the 4.0. . .so I won't be able to get at least the same speed going Internal? Then perhaps size limitation? I cannot find as a "Matter of Fact" how Large can I go [8TB]?

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Well folks. . .feel free to read the whole thread of both lines of conversation - perhaps you’ll pick up something I missed; but since I can’t vote yes on “Problem solved” for Both, then I can’t rightly select that for either – because BOTH are right, in its proper context.  I will explain. . .

EXP:  Dan is speaking from a Highly Professional point of view; and, really everything he is saying is Technically correct [to the best of my ability to verify].  However, being “right” doesn’t ALWAYS mean the opposing view is “wrong”.  What is true as viewed from the East side, might not be so true when viewed from the West side.

As you can see, I frustrated Dan at the very end, as I was trying to pull out of him what he actually knows.  He spent too much time repeating himself, most of which was unnecessary, but, somehow, I just wasn’t able to communicate my exact questions that needed answered, so he re-answered some things, others he didn’t answer at all.

The BOTTOM LINE IS: In reviewing different sites, even in the Q & A section, on the much touted “Apple’s Proprietary SSDs” as well as in reviewing Amazon’s 1000’s of users who have successfully installed an adapter to iMacs and MacBooks to be able to utilize the M.2 PCIe. . .MOST of these agree with Simon’s recommendation.  One has to believe that if the outcomes tended to end up as complete failure of the SSD in 9 month’s there would be MUCH more posts out there reflecting this. . . Fact is, I DON’T see Any!  Therefore, I HAVE to conclude that Simon’s point of view is “Practically Correct” . . . it DOES work AND it can work, over long-term.

Furthermore, I believe I verified different times with Dan [This is the ONE place I did specifically ask for him to repeat himself], the explanation for the large amount of the SSD failures he has seen, is highly likely due to:

-Small Drives

-Drives filled too full

-Extensive Read/Write usage

-Too limited RAM, increasing Virtual RAM writes to SSD.

These are the NO-Nos listed for any NAND technology, including smart phones.  SO. . .the question that remains is:  “Is this because of the M.2 Adapter OR is it because of improper SSD use [not understanding it’s limitations]?”.

Since, according to Dan AND everywhere else I have looked, other hardware, software failure, Panics, etc. are NOT the result of an M.2 adapter; to me, this actually lends credibility to its ultimate compatibility and the acceptability of adapter usage.  NOT that no one had any such problems, but from what I have seen, there is a fix for all of them; and for the few that there might not be. . .is it possible with all of the reported success, that these might be counted up as defective adapters; SSDs OR operator/installer error?

Another thing to mind, and I sure wish I could have gotten Simon to respond to my queries on this, but there is NO DOUBT that there are good and bad M.2 adapters.  Some, inexplicably reduce the throughput by utilizing only 1 Lane!  So, the proper Adapter, working in conjunction with a compatible PCIe, IS CRITICAL to making this a “happy ending”.

I am sure that Dan will believe that I slighted his knowledge, but this is FAR from the truth.  His knowledge, very much, helped me come to this conclusion.  Just because I don’t come out at the same point, doesn’t mean that I ignored his advice.  I just wish I hadn’t “worn him out” and caused him to give up on me.  I haven’t given up on him; he certainly knows what he is talking about.

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You glossed over the hardware difference and how the OS has a big part in how wear leveling works.

You also failed to point out different uses of the user (work flow) has a bearing here as well. As I stated I’m not a hater of M.2 SSD’s it’s the difference of a force fit (adapt) that is incomplete Vs a design that is 100%.

Think of it this way… you can add a bit of gasoline into a tank of diesel with no problem but a bit too much and bang! The engine explodes!

So… How much is to much? Or is it better just to get the diesel instead of taking the chance?

Many of the asks where at a much deeper forensics level into the failures than I’m even equipped to perform. I even expressed that clearly. Even still it doesn’t take much to make a correlation of failures to see a pattern. That’s what I saw and others have as well.

You need to dig into the core documentation both from Intel and review the schematics for the Apple systems to see how things work and then study the M.2 standards. As I stated I can’t educate you on all this stuff this is not a school we are strictly here to help get gear working and through that people can pickup quite a lot!

Clearly, it’s not the answer you wanted to hear, I get that! Being safe is a lot different than being reckless. The systems I fix are for people who are safety nuts as their employment depends on reliability.


@danj-Hi Dan. No intention on "glossing over" anything. That's why I invite all to read the entire thread; all can make up their own mind with the facts and advice given. It definitely appears a User "environment" thing - "How will it be used?". And even your current comment, STILL exemplifies this. The "garbage collection" is not disabled, just slower. So give it space to breathe. For the high-end video/image work, it has become MORE clear to me than ever-Thanks to YOU, that a Single SSD, of any type and speed, stuck on an internal board, is not appropriate for continuous use of this type, and WILL fail. SSDs cannot handle the R/Ws; this is a KNOWN limitation of NAND.

I VERY intentionally, go into every question, WITHOUT my mind made up. I have nothing to win on this, I am really in doubt as to whether I will do this, as it appears that I can get faster throughput by going 4.0 PCIe at TB3 port. So this isn't a matter of "what I wanted to hear"; but I speak to the original ?. . .will it work. YES.


@mandm_0 - Nope garbage collection is a bit more complex! Wear leveling is tied to the hardware with Apples custom SSD’s not so with the M.2 SSD’s. With M.2 drives the system needs to be shutdown so the open files are released. With the Apple SSD’s leverage APFS snapshot feature which allows at the file system a clone of the open files releasing the lock on Set-A and enable the lock on Set-B without missing a beat!


@danj-SEE what I SAY. . .YOU are a wealth of wonderful knowledge! I was thinking on my way home from work[takes an hour], that there were MANY questions that you answered for me, throughout this research that I am truly grateful for; and I have no doubt will help many, if they take the time to read through it all.

This tid-bit, you did mention before; but the context is a little better for some, I expect. I got it the first time; but I don't mind the repeat. I certainly don't know about everyone on this, but I am satisfied that my computer has to be restarted enough to accomplish what the M.2 needs. And what I have in mind on this, is NOT just restart; but the ratio between restart and the need to deal with deleted files. AS we both said . . .our SSDs hold System and Static files. . .so LITTLE garbage. IF my Puter is restarted every other week, with the little garbage to deal with - I feel confident all will be well.

But again, this is coming down to personal computer use and config.

Thanks Man!


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@mandm_0 - That’s a lot of Q’s!

Apple uses a hybrid design using the PCIe lanes and NVMe protocol for the data storage. But the way any SSD does wear leveling and housekeeping (garbage collection) chores are not set in stone! Each vendor does their own thing within the SSD’s micro controller and firmware. This is the bugaboo! As Apple did their own thing and as they also do the rest of the system hardware and OS they did some funky stuff! The systems firmware has also changed so what they did day one is a bit different today and the given series also gets into this.

All I can tell you is I’ve pulled out a lot of M.2 drives and their adapters out of many systems! These are mostly pros and advanced amateurs in music, photo and video work.

So… what I recommend is sticking with the Apple or OWC drives for the blade drives which you can get upto 2TB. The way you use your drives has a big bearing on the systems performance. I recommend using the blade drive as your boot drive and hosting your apps. Don’t load it up with junk stuff lean and mean! Leaving at least 1/3 of the drive unused! The more the better if you work on large projects so the OS can cache and if needed use the free space for Virtual RAM if your Physical RAM is not enough. Having more also allows some apps to use it for scratch space.

Now getting into the external ports your system only offers two Thunderbolt3 (USB-C) ports, so what you plug in for a drive becomes tricky! As an Apple based TB3 drive offers better throughput than a generic PC USB-C drive! But even that is not using the full ability of the I/O channel! This is where RAID setups make a sizable difference!

So… where does that leave us? Use the internal blade drive for your OS and Apps leaving enough free space for Caching Virtual RAM and if you use apps which use scratch space, and consider your workflows needs. I would use the Internal SATA port to hold my media and static art. And then use a RAID set for my active work (which is what I do)

The version of PCIe is 3.0 per Apple.

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@danj THANKS for your expertise! Still a few questions left in the frontal lobe. . .What you are meaning is that the M.2 and adapters were worn out from use? Do you know what the Throughput of the Apple 3.0 is? Here is part of my quandary. . l use my HDD for all of my constant Scratch/Read/write work; I have an overabundance of RAM, so zero page-ins/outs; I keep HDD HFS+ and SDDs-AFPS as I don't believe the two formats should be mixed [causes early HDD failure]; virtually ALL of my static data-Music, Apps, System, Video. . .all read-only stuff on SSD [PCIe]-with 1/3 left unused . . .IS the failure you are seeing Actually because SSDs are still prone to early failure with constant read/write AND because people tend to overfill them - because with many going completely SSD, they DON'T have the space? I am trying to zero in on what actually is the Cause of what you have witnessed. You have GREAT points; but is there more to it? I have been telling people for some time that they will regret SSD only.


@mandm_0 - Apple produced a few different ones over time so people often forget that. So the newest gen is the SSPOLARIS which is the one I put in. OWC also has a few generations which also is a factor. I would go with OWC Aura Pro X2 SSD sadly Apples SSD’s are a bit dated as they dropped replaceable drives in the M series systems.

Blade SSD failures I’ve seen is often lack of free blocks related to how Apple does wear leveling and garbage collection. Apple uses a pin in the socket to communicate with the OS which the M.2 and adapter have no idea! So the OS pumps data to the SSD before its had a chance to breathe. Which is also why on a SSD boot drive (any) I always have at least 1/3 free space so the rate of wear leveling is high enough not to write on an already worn block/s.

And, yes I’ve seen drives which are overloaded too (all kinds of SSD’s) my own 2012 15” MacBook Pro drive went on me the other week. I was working on a large document with tons of images before I knew it the 4 year old 1TB drive went on me.


@danj -So. . .again. . .and I am still guessing here. . .the M.2 and Adapters "Failed", which is why you hand to yank them. . .any Idea of how long they were in Service before this happened? [I say I am guessing because there is a host of things that could have happened that you might also be referring to, such as that you had to replace them because they grew considerably slow, or became non-bootable/fixable, yet being an operational SSD otherwise; ceased to be recognized by Hardware, etc.].

Are you aware of an ACTUAL size limitation at the PCIe HUB? I am at 20TB on my HDD. . .but theoretically, IF an adapter could actually work is there a known hardware/firmware limitation on the size of a workable/bootable PCIe SSD at the internal connection?

I think perhaps you said it, or maybe somewhere else I read it, Apple didn't go M.2 because it wasn't theirs. They want to maintain an exclusive vendor; but by doing so, they are forcing a certain, dedicated consumer base, to go in different directions.


@mandm_0 - Do be careful! Someone who chirps up once with no cred is not your best source, best to review their info card.

As I stated my clients are pros and advanced amateurs who work on their systems quite heavily. They too got the idea is was safe and for light users it will take a bit of time before the S hits the fan, so consider your use case. If you had a MacBook Pro it’s a lot easier to get to than an iMac.

To answer the added questions. It varies on the drives size the small ones go sooner. Six to nine months for most of them. A good sign of pending failure is getting a hang or problems rebooting.

The few I was able to get going after failing showed incomplete write events which could be the adapter slipping or shorting out.

Sadly, once dead it’s dead! There really isn’t anyway (as far as what I have for tools) to poll the micro controllers block DB to see what’s happening with the reserved allocation or if there was a block/s failure. I know it can be done with custom tools and having much deeper info into the given drive. I don’t have the time or needed skill level to do that level of forensics.

Think of it this way you have a bunch of light bulbs burning out way too soon should you dissect them to figure out why they failed or should you give them the basic testing and then call it a day. You might look at who’s bulbs or what is different between the working and non-working and if there was any common thread assume that was the most likely cause of failure.

I can tell you I don’t see many Apple drive failures and not many OWC either.

And lastly, having the fastest and most expensive car doesn’t help you when you are stuck in traffic either! So don’t be so quick to assume you need the fastest drive internally. For me the active data drive is more important. So I’m not looking at beach balls! And I have a ton of RAM (64GB)


What do you mean by PCI hub?

The PCH chip is all there is and we talk about PCI lanes a given port or device has.

As far as drive limits MacOS can support over an ExaByte of drive space! You would be hard pressed to get to that 🤔

Internally the blade interface is PCIe 3.0 x4 NVMe. The physical limit of the drives real estate limits the drives size and there is a point the limit of four lanes also plays a factor when you get into the larger sizes (as well as the costs) in theory with the way chip shrinkage is going it’s likely possible in a few years to get a 16 or even a 32TB drive 1Tb flash chip but that will be in an M.2 drive not a custom Apple SSD (if done). More likely the interface standard will be different as one of the costs of these dense drives is heat! In the Server space we have a very different architecture in storage (SAS) these ultra large drives will more likely use that interface than M.2 and offer a sizable heatsink more in the size range of a stretched 2.5” drive physically here’s a bit more Difference between SAS vs SSD


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Just use a M.2 SSD and a adapter than you have full 3.0 Speed. Faster than the $@$* OWC SSD for internal use

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@ich558 - You need to be careful! Without a deep understanding on what’s going on and which system/drive you might have had better options!

I don’t hate M.2 drives! In fact my SSD RAID is a set of 2TB M.2 SSD’s as they are very good! But this is not the same here, as here we are fudging it! Where my RAID box was designed with them in mind!

Apple should have gone with the M.2 spec’ed drives as that would have been so much better!


@ich558 -I am just wondering. . .have you tried this? Is this a part of your Production System configuration? If so, how long have you been using it this way? Could you give specifics as to actual devices used, size of SSD, etc. AND. . .you are saying that you are getting, is that 1600/1800 read/write speeds?


@mandm_0 i upgraded hundreds of iMacs with M.2 SSDs. Up to 4TB are no Problem. Also 8TB but these are expensive. There was never a problem. You can also upgrade to a i9 9900 3,1 GHz.


@ich558-Thank you for that verification. I assume that you did not get any of these back with problems; within a reasonable amount of time? Is there any firmware updates/issues that you saw?

It looks like I was low in my guess, according to the much touted article, the 5th Gen 3.0 should deliver ~2,700 MB/s read speed and ~2,350 MB/s write speed. . .and you are saying that WITH the M.2 adapter, these speeds were basically realized? I saw one adapter that cut the speeds in HALF. I definitely DON'T want that.

Is there an Adapter brand/model that you found best to use, same with any recommendations for a PCIe NVMe-M.2 or specific ones to avoid? [I actually do have the i9 9900 3.6GHz.]


@mandm_0 there are no problem at all. Thats why the 2017 and 2019 imacs are still a good value. If you use the "good" SSDs you can get up to 3500 mb/s speed (which is the maximum pcie 3.0 speed). Actually, I never had a reduced speed when using cheep adapters, but you can use the Gigabase adapter for sure


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