Case For Unfusing the Fusion Drive

[varian55zx]

Upon realization of the level of simplicity in the process, I opted to unfuse my 2tb fusion drive with the late 2015 iMac 5K.

This seems to be a somewhat controversial move, in that many seem to be against it, and many users have been unhappy with the split. To me, though, it always sounded like the better option.

As soon as I spent some time with Fusion drive, I noted various imperfections with it or certain aspects that I had an aversion to.

Another point to add, is that I actually enjoy the management of files, on a somewhat casual level. It is something I do for somewhat of a hobby anyway, or have over the years. It more or less equates to the digital version of housekeeping, the organizational angle to it is something that I am not altogether opposed to.

Add in the fact that I always (in my usage scenario) will want certain things on the SSD and certain things on the HDD. For example, media such as music and TV shows. I never want those on the SSD. Terrible idea.

I recently did a mass import of several seasons of shows and it seemed that some shows remained sitting on the SSD. Ok, well that's not good. That's a complete waste of space.

For any of my itunes files those won't ever need to be on the SSD. The reality is the only data I will ever want on the SSD are system files, the OS itself, and applications.

Management on that level is possible with a split, and impossible without. Now my massive library of data can be stored on an internal HDD (don't have to rely on an external) and I have the equivalent read speed of a 256 SSD.

Another point to add is that with the split, I can manage how much data is on the SSD. If an SSD regularly only has 4GB available, its performance will suffer from being so bogged down.

My SSD has over half its space left after all my system files and applications have gone onto it, and I plan to keep it at about that level to maintain the speed.

Having that much free space on the SSD is not possible without an unfuse.

I believe unfusing the drive allows you a level of control that is not possible without doing so, and believe it to be undoubtedly superior to a fusion drive.

 

[circatee]

This seems to be a growing argument, i.e. 'give owners' the option to 'unfuse'.
But, from my understanding, the more you use the Fusion drive, it learns your habits, and thus places the more used items on the SSD portion. Thus the likes of iTunes 'stuff', probably wouldn't reside on the SSD portion, unless you're using it a lot.

On another note, can you post the steps to defuse, for others?

 

[varian55zx]

This seems to be a growing argument, i.e. 'give owners' the option to 'unfuse'.
But, from my understanding, the more you use the Fusion drive, it learns your habits, and thus places the more used items on the SSD portion. Thus the likes of iTunes 'stuff', probably wouldn't reside on the SSD portion, unless you're using it a lot.

On another note, can you post the steps to defuse, for others?

I'll add some input to this.

Owners do have the option to unfuse. It's actually very simple.

Unfusing itself took about 2 minutes. But you have to reinstall El Capitan after that and that took about 30 minutes, then you have to restore from your Time Machine backup which took some time as well.

That wasn't that great. But the end result is great, especially for someone like me, who didn't want to really use externals (besides my backup drive).

I'm much happier with this arrangement so far.

Fusion does learn your habits and I actually won't speak badly about the software, because it is actually objectively 'good'.

But it's not perfect and certain things will remain on the SSD that simply shouldn't be there.

But, another point to add, is that as I understand it, the fusion software will regularly only leave 4gb available on the SSD which would make for a noticeable speed decrease.

I have >60gb free on my 128 SSD, so that won't be a problem.

 

[JustMartin]

I haven't done any benchmarks or much research here. What's the difference in speed between a half empty SSD and one with 4 Gig free and how does that speed compare to a hard drive access? I just look at 60gb not used on your SSD and think that's a waste of perfectly good fast disk. Mind you I'm happy with my fusion drive and not interested in managing it at all myself.

 

[varian55zx]

I haven't done any benchmarks or much research here. What's the difference in speed between a half empty SSD and one with 4 Gig free and how does that speed compare to a hard drive access? I just look at 60gb not used on your SSD and think that's a waste of perfectly good fast disk. Mind you I'm happy with my fusion drive and not interested in managing it at all myself.

I'm glad you are happy with it, frankly I was too. My aim is not to try and make anyone "go my way" because it's "better".

I merely am offering a point of view.

I wanted that 60 gb free to maintain speed, as I understand it, it has been proven that SSDs show a speed decrease once a certain percentage is filled up.

This article from howtogeek explains why:

http://www.howtogeek.com/165542/why-solid-state-drives-slow-down-as-you-fill-them-up/

So given that, that would be a factor present in the fusion drive, understated as it may be.

I can't speak for everyone, but I'll only be using my internal hard drive to store media and document files. Media being music and TV shows and some movies. I don't believe HDD vs SSD speeds will matter there, we're talking about the simple opening of video or .docx file.

Won't make a difference.

I just wish Apple gave an option for something like an internal 256 SSD and 2tb hard drive.

 

[varian55zx]

Here's a screen of the Blackmagic test for the SSD portion of the 2tb fusion drive.

It's hitting 1800 mb/s reads.

 

[maflynn]

I was also tempted to unfuse the drives, but as I contemplated the benefits and consequences, I realized that while I would improve some of the performance of the computer, overall it may be slower.

To put it another way, I'd be on the hook to decide what sits on the small 128GB Fusion drive, and what's on the spinning hard drive. I think I'd be doing a worse job of deciding then OS X.

My first knee jerk reaction would be to split the SSD in half, 64GB for OS X and 64GB for Windows. As I thought about it, I realized this will be too small to adequately run both operating systems over the long haul. Perhaps, if I get a USB 3.0 drive and put my windows system on that, then that makes sense and then use the spinning drive for data.

The downside with that setup, is that it complicates my backup strategy, as I want to be able to easily backup and restore my system. Having multiple disks and volumes makes using CCC that much harder.

 

[varian55zx]

Since I don't use Windows, I won't need to partition the drive. That means that I basically have 120gb of space for a 'boot' drive more or less.

On the SSD I have my Applications Folder, Library, System, and users folder. That's it. I have 64 gb of free space on the SSD, but that's just the thing. For me, that is all I ever am going to want on the SSD.

The spinner has about 800gb of essentially media on it. These are music, video files, or whatever else. These are all files that never need to be on the SSD under any circumstances, because you won't even see a speed increase if they are.

There's no speed difference between opening an avi tv show from the spinner vs SSD, for example.

Every new file that I obtain will be routinely organized (by myself). Most files will go to the spinner. I have a small folder for files I keep on the SSD that has a few documents and the like (just because I have the space).

I'm not sure if this will apply in all usage cases, but for me, every file that will benefit from the SSD is on it, and everything else that wouldn't need to be on the SSD because there would be no noticeable increase, is on the spinner.

I am now getting SSD speeds and can still only rely on internal storage (which was the point of me getting the fusion drive).

With 1800 mb/s read speeds this thing is really fast now. I'm extremely pleased with the results.

 

[maflynn]

Since I don't use Windows, I won't need to partition the drive. That means that I basically have 120gb of space for a 'boot' drive more or less.

If I don't use windows, that definitely simplifies the process and you can easily make the case of splitting up the drive. It still means extra work for backing up, if you use products other then Time Machine as I do.

 

[varian55zx]

If I don't use windows, that definitely simplifies the process and you can easily make the case of splitting up the drive. It still means extra work for backing up, if you use products other then Time Machine as I do.

Yeah actually that is why I was so open to doing it, since I don't use Windows, I knew there would be a lot of space leftover. And there is, I'm just under half full on the SSD and I'm done loading things onto it. Nothing else needs to go on it.

If I had Windows as a consideration there is a definite possibility I wouldn't have done it.

 

[maflynn]

My user account has over 660 gigabytes of storage being consumed, but the system and apps would easily fit.
If I dig down deeper.

I'd have to move my pictures, specific folders in the Document folder (winclone backup and VM) and my music folder to the spinning drive. My Library folder is huge and digging down in that, it looks like I have a number of iPhone backups that may need to stay

 

[varian55zx]

My user account has over 660 gigabytes of storage being consumed, but the system and apps would easily fit.
If I dig down deeper.
View attachment 633999

I'd have to move my pictures, specific folders in the Document folder (winclone backup and VM) and my music folder to the spinning drive. My Library folder is huge and digging down in that, it looks like I have a number of iPhone backups that may need to stay

In my case I kept my whole library folder on my SSD.

My library folder is 12.7 gb so I can easily afford to. Anything like pictures, documents, and movies or video I put on the spinner. There isn't even a speed increase from having it on the SSD so that is something I wanted to do all along.

And say you were doing an editing project, you can simply move the file to be edited to the SSD, edit it, and then put it on the spinner for storage.

I'm doing housekeeping now that I didn't do before, but I actually enjoy the management angle of it.

Of course what makes it worth it is I'm getting SSD speeds now. Everything is noticeably faster, near instant.

 

[circatee]

Did you use an app or setting on your iMac, to get the details of the directories, in your image?

My user account has over 660 gigabytes of storage being consumed, but the system and apps would easily fit.
If I dig down deeper.
View attachment 633999

I'd have to move my pictures, specific folders in the Document folder (winclone backup and VM) and my music folder to the spinning drive. My Library folder is huge and digging down in that, it looks like I have a number of iPhone backups that may need to stay

 

[maflynn]

I used Omnidisksweeper. Its a handy little app

 

[Fishrrman]

OP wrote:
"Here's a screen of the Blackmagic test for the SSD portion of the 2tb fusion drive.
It's hitting 1800 mb/s reads."

VERY impressive speeds!

If one doesn't mind "managing" where one's files go, one could "de-fuse" the factory setup and enjoy these speeds all the time.

Some care would need to be exercised to prevent the SSD drive from getting too "crowded", so that enough free space would be left to keep the drive performing at its optimum...

 

[maflynn]

VERY impressive speeds!

Definitely, but to play devil's advocate, those that have the Fusion drive already enjoy those speeds. My boot up is wicked fast, my apps come right up, with a minimum of bouncing. So basically any data blocks on the SSD are enjoying that fast throughput. In a sense, you can justify that non-splitting because the OS does such a great job at managing the space.

 

[varian55zx]

Yeah, but that's just thing. I actually think the OS doesn't do such a good job of managing the space. I do a much better job.

The OS will move things onto the SSD that don't need to be there, and once the SSD is more than 75% full, it's speed will decrease.

I keep all my media files on the HDD because they wouldn't even benefit from a speed increase from the SSD. By doing it I keep SSD space free which means it will operate at peak performance.

The system is also 1000% faster in daily use. Everything opens in one bounce now. Web pages load instantly. Everything is fast.

I'm now getting SSD speeds instead of fusion speeds, so I'm happy about it. And I still get the internal storage which is why I went for the fusion in the first place (hate external drives).

 

[maflynn]

The OS will move things onto the SSD that don't need to be there, and once the SSD is more than 75% full, it's speed will decrease.

Do you have details of its moving that you don't want moved? Also are you sure its filling up the SSD?

I have to believe the folks at Apple understand the basic concepts of the SSD and keeping it from filling up, must be part of the logic. I have no way to confirm this, so its more of an assumption.

Don't get me wrong, I've been tempted to split up my Fusion drive since I got my iMac, but as I visit and revisit the topic, I can't justify the work, i.e., will it make my computing experience better in terms of performance and management of the computer (dealing with my files, and day to day usage)

 

[sartrekid]

Here's a screen of the Blackmagic test for the SSD portion of the 2tb fusion drive.

It's hitting 1800 mb/s reads.

I am getting the same results by running the test on the fusion drive. So, the OS does seem to pick the SSD anyway for such tasks.

 

[hfg]

If you have stuff that you absolutely don't want to ever be on the SSD portion of the Fusion drive, you can easily use BootCamp Assistant to create a partition (normally used for Windows), but instead simply format it for OS X and put whatever you want there. It will not be managed by the Fusion software for speed, but is fully accessible as normal storage.

I am also a bit confused by the comments that SSDs slow down as they fill up. With current SSD being over provisioned and OS-synced TRIM, there shouldn't be a problem for normal consumer usage (read-mostly). Hard disks demonstrate this issue due to the slower linear velocity on the inner tracks with rotating platters as they fill up with data. SSDs used in Enterprise data base systems (write-mostly) would be more concerned with max-capacity slowdown issues.
[doublepost=1464969599][/doublepost]

I am getting the same results by running the test on the fusion drive. So, the OS does seem to pick the SSD anyway for such tasks.

The Fusion drive reserves a disk-write cache buffer on the SSD prior to writing the data to the hard disk. If your disk-speed test block size fits within this buffer, you will certainly see SSD speeds as it is, in fact, reading and writing to the SSD reserved buffer. There are caveats with using BlackMagic speed tests since they are designed for video performance on large incompressible files rather than the random access small block transfers where SSDs excel. Different test programs can give more realistic results for actual usage results, but BlackMagic is readily available and convenient for sharing test results.

 

[varian55zx]

I have no interest in proving just how good the speed increase from splitting it is (it's soo much faster).

You can either take my word for it or not. It doesn't matter, because I know I'm right (very obvious).

Do you have details of its moving that you don't want moved? Also are you sure its filling up the SSD?

Sure I do. Fusion leaves 4gb left on the SSD. It automatically fills the rest up with whatever it determines to be the most frequently used files. So, since, as you have seen, I only want >60gb on my SSD, it's moving a huge amount of files I don't want it to.

I have to believe the folks at Apple understand the basic concepts of the SSD and keeping it from filling up, must be part of the logic. I have no way to confirm this, so its more of an assumption.

I think they knew that SSDs slow down once they're 75% full, but didn't let that stop them from implementing the fusion technology. I think they probably thought most people wouldn't notice/care.

Don't get me wrong, I've been tempted to split up my Fusion drive since I got my iMac, but as I visit and revisit the topic, I can't justify the work, i.e., will it make my computing experience better in terms of performance and management of the computer (dealing with my files, and day to day usage)

I thought somewhat of the same way, but it's not work.

One terminal command and they're split. Then you just have to reinstall El Capitan so the system doesn't detect the two drives as a fusion drive that has been split.

Download El Capitan, make some microwave popcorn. And it's done.

Of course you also have to migrate all your data from your backup to the HDD, but you can just do that overnight.

Say you don't like it, you can rejoin them just as quickly. In my case, I preferred it. So I kept it.

I am getting the same results by running the test on the fusion drive. So, the OS does seem to pick the SSD anyway for such tasks.

Maybe blackmagic is showing those speeds for you, but I'm actually getting them.

If you have a fusion part of everything is on the SSD, and part of everything is on the HDD. That's just the advantage for me, everything I want on the HDD, all of it is on there, and vice versa.

 

[toddzrx]

Being that I installed an SSD before Fusion Drives were released, I've always had 2 drives: an internal 120GB SSD, and then a 1TB portable external drive. I only put media on the spinner, while the OS, apps, and all other data (documents, pdfs, etc.) stay on the SSD. To me, it works great, even though I'm on SATA 2 speeds. I too prefer the manual file management that comes with this setup, but quite frankly, after putting everything in its place the first time, there's very little managing that has to be done. And I barely notice the "slowness" of the spinner because it's only accessed when using iTunes or Photos.

 

[varian55zx]

Being that I installed an SSD before Fusion Drives were released, I've always had 2 drives: an internal 120GB SSD, and then a 1TB portable external drive. I only put media on the spinner, while the OS, apps, and all other data (documents, pdfs, etc.) stay on the SSD. To me, it works great, even though I'm on SATA 2 speeds. I too prefer the manual file management that comes with this setup, but quite frankly, after putting everything in its place the first time, there's very little managing that has to be done. And I barely notice the "slowness" of the spinner because it's only accessed when using iTunes or Photos.

This is exactly what I'm doing, and exactly my same experience.

The only difference is his drive is an external drive and mine is internal. But they're both being used for the same uses and are separate from our OSs.

When you use this method you can use the HDD for storage as it's meant to be used for, and then the OS and all the system files are on the fast SSD.

Nothing will move unless you want it to. But he is correct in that there is very little file management after it's all set up. I don't think I'm even managing files more than when I had the fusion drive.

 

[sartrekid]

Maybe blackmagic is showing those speeds for you, but I'm actually getting them.

If you have a fusion part of everything is on the SSD, and part of everything is on the HDD. That's just the advantage for me, everything I want on the HDD, all of it is on there, and vice versa.

That might very well be the case and I'm not doubting your findings in any which way. I am still on the fence on whether to do it the way you have or not. What I don't understand is, why does the Fusion drive exist at all if tasks that would benefit from the SSD portion don't make use of the SSD? What's the point, then, of having a Fusion drive in the first place?

My iMac is pretty new. I bought it about two months ago. My main use are programs such as Photoshop and the like. All of my apps open instantly with the exception of the Adobe CC software. As I understood it, the SSD will be utilised for tasks I do often. Photoshop is one such app that I use the most and yet it still takes somewhere between three and five bounces before it's ready. Could it be that this is the compromise I'm seeing? Shouldn't the most frequently used apps load faster?

I do use Bootcamp, so I'm really wondering what would be the best way to go about it. I had thought about using an external SSD for Bootcamp and OS X boot drive. I say this because I'm unsure whether the 128GB would be sufficient to be used as a boot drive for OS X and all the apps.

 

[varian55zx]

That might very well be the case and I'm not doubting your findings in any which way. I am still on the fence on whether to do it the way you have or not. What I don't understand is, why does the Fusion drive exist at all if tasks that would benefit from the SSD portion don't make use of the SSD? What's the point, then, of having a Fusion drive in the first place?

My iMac is pretty new. I bought it about two months ago. My main use are programs such as Photoshop and the like. All of my apps open instantly with the exception of the Adobe CC software. As I understood it, the SSD will be utilised for tasks I do often. Photoshop is one such app that I use the most and yet it still takes somewhere between three and five bounces before it's ready. Could it be that this is the compromise I'm seeing? Shouldn't the most frequently used apps load faster?

I do use Bootcamp, so I'm really wondering what would be the best way to go about it. I had thought about using an external SSD for Bootcamp and OS X boot drive. I say this because I'm unsure whether the 128GB would be sufficient to be used as a boot drive for OS X and all the apps.

Well, to elaborate on this, the fusion drives works in terms of blocks.

It will move blocks of files to the SSD from the HDD and vice versa. It doesn't move the whole thing, so that is why I say only part of the app will be on the SSD. But that's just the thing, in too many cases, you will want all of the app to be on the SSD. No need for the software to move blocks of it over to the HDD.

Apps open fast with the fusion drive but they open faster when you're just running off the SSD alone. Photoshop for me now opens in probably less than 2 seconds, took 2 or a little more before.

The best example I can think of is system preferences. It always opened in two bounces which really bugged me. Now it always opens in one now that I'm running off an SSD.

They all pretty much open in one bounce now. Everything is much faster, web pages load instantly. Folders like my applications folder load instantly. Pretty much every possible thing you can do is sped up. Oh, and spotlight is so much better.

As for the boot drive I still have just over half left with my OS, system files, and all my apps, so 120gb works for me. Guess I got lucky there.

edit: confirmed photoshop in one bounce and less than 2 seconds. Compare that to 4 bounces and over 2 seconds (but less than 3) with the 2 tb fusion.