[kevs]

I 'm poised to buy a new 27" (my old one is 6 years old). In the Apple store today the rep said the Fusion drives only have 24 SSD on them and the rest it old style platter -- about.. 40 to 1 ratio!. Yet online Apple says it this type of magic drive knows what you have been using and opens it up with SSD. I was leaning toward just getting a 500GB SSD which cost more, but want to ask how fusion works first, he could not explain that well.

Also, he kept saying the OS is only 4GB. But on my macbook air (60GB Mac HD) it keeps running out of space (will be replacing soon), and all I have on that is 10GB of apps and 5 GB of imap mail. That's it!
The rest is Library, system, and other hidden obtuse system things like Private folders which I have no idea what is in there. So to me there the OS is taking 40GB for all intents and purposes.

Finally, the consensus seems to be 16 GB Ram is enough? And don't buy Apples, save $ and go crucial?

[Mike Wuerthele]

Fusion drives are nice, and real-world between 60-80% the speed of an all-SSD solution. If you've got the money, go all SSD.

16GB of RAM is enough. No need to buy Apple's.

[P]

Fusion Drive is a smallish SSD plus a big HDD. If you get the 1TB Fusion Drive, you get 24 GB SSD plus 1TB HDD. If you get the 3TB Fusion Drive, you get 120 GB SSD plus 3TB HDD.

Basically the idea is that the most used stuff is kept on the SSD, plus a small buffer to handle writes. In practice all writes that are not insane will go to the flash and behave as if done to an SSD, and all reads that fit in the flash will come from the flash and behave as if it were another level of disk cache (although it technically isn't a cache, but don't get me started on that). The OS is pretty clever at figuring out what needs to be in the flash - after all, it already does that for the actual disk cache in RAM. The bits of the OS that you need over and over again are small - far from the full installation - so a 24GB flash in a Fusion Drive will make a real difference.

In fact, when these hybrid drives started to be a thing on the PC side (they were all in hardware and less clever, only caching reads), they started out at 4GB. These days they're generally 8GB. 24GB exist, but that is the largest available. Intel launched a solution to let everyone build their own caching hybrid drive, but configured it to accept no more than 64GB for the caching SSD - because they saw no real performance gain from going bigger. A full SSD is of course even better, but as a rule of thumb, the miss-rate for a cache goes as the square root of the size of the cache. For a laptop, a true SSD makes more of a difference because spinning up the HDD drains the battery, but you don't have that concern on a desktop.

I think the best way to sum it up is to say that in normal usage, you won't notice a difference. When torturing the iMac, the SSD will be better. Do you often torture your iMac by maxing out the drive I/O? If so, get an SSD. If not, Fusion Drive will be fine.

IMO, 16 GB RAM is fine, and any RAM you can get is equivalent at this point (at the speeds the iMac will operate).

[turtle777]

I have been amazed by the Fusion Drive in my iMac. Feels like SSD most of the time.
Do not regret not getting a full SSD.

-t

[kevs]

Thanks Mike and P,
Darn, P did not understand that too much, will try to re-read a few times. Oreo on this site says definitely get 500 SSD. But I want to spot check. Feel free to jump in Oreo. I went to store today so had to ask, very confusing the whole thing.

Now the guy at the store said something that I would only understand had I gone there: when you decide to go 500 SSD that is your hardrive, it's either all SSD or Fusion with just a little SSD.

Then another thing just learned is this correct: that the Fusion only works for the OS, not DAta, where if you get pure SSD then you get the benefit of fast start up times (OS,) and also fast loading times for images (date), is that correct? HOPe that made sense.

Also, please, my OS on my laptop seems to be 45 GB but guy at store says the OS is 4 GB?


Thanks Turtle, did not see your post till after I posted, ok, thank, how does it work? AGain,, wont help with images, just the app speed?
Thanks Turtle, did not see your post till after I posted, so how does Fusion work? Still don't get the magic.. but it wont make opening images faster just app speed?

Finally: the imca 27 only comes with 8 GB, 2 4's -- they charge $200 if you want 2 8 instead. Crucial sells 16 for only $35, but don't get how many stickes, maybe I should call them..

[reader50]

Your iMac has two internal drive bays. A smaller one for an SSD, and a bigger one for an HDD.

If you ordered with the plain HD, you get:
the SSD bay: empty
the HDD bay: 1 TB HDD

If you order it with a pure SSD, you get:
the SSD bay: 250 or 500 GB SSD
the HDD bay: empty

If you order it with a Fusion drive, you get:
the SSD bay: 24 or 120 GB SSD
the HDD bay: 1, 2, or 3 TB HDD

With Fusion, OSX stitches together the SSD and HDD into one volume for you. In the background, OSX will fiddle around what files are stored on which drive. You won't see any of this, you'll just see the one big volume.

OSX is fairly good at placing your commonly-used files on the SSD side, so they'll open really fast. This includes files used in booting up. So most of the time, the Fusion drive will be as fast or nearly as fast as a pure SSD.

Should you start saving media files on your drive (movies or TV shows) the extra size of the Fusion drive will come in handy. The 500 GB pure SSD is rather pricey - the 3 TB fusion costs less and has six times the space available.

-------------

A plain OS X install can fit in 5 GB, but once you start using it, 40 GB is more reasonable. Should you add personal and work files, perhaps 100 GB, perhaps a great deal more. Depends on how big your files are, and how many you keep on hand. Always assume you'll have more files in the future.

A music library will add a few gigabytes. A photo library (jpegs) will add a few more gigs. A photo library based on RAW photos will add a lot of gigs. Video files add a lot of gigs.

We can't guess at how much you'll want to store, just that it will be more than you expect. I'd recommend taking the storage space you're using today, and multiply by at least 4 times, perhaps more. If that total will fit in 250 or 500 GB, go for the SSD. If the multiplied total is close to 500 or higher, get the Fusion so you'll have the elbow room in the future.

[kevs]

Thanks Reader, that helps clarify things a bit. I have not see any of that on the Apple site, the bays and how they line up! Why don't they list that.. is there a link to it?

Ok I have now on 27" the one TB, 6 years old, it's OS is on the MacHD and I don't use the rest of that hard drive for anything.
My Main external is 3TB, with backups up to another 3TB clone, and I have a 3rd 3TB clone off site. This is full about 2.5. TB, and 1tb of that are photos that I hardly ever use. These externals are all about 5 years old, so I should replace them. Maybe I could put that 1TB of photos I hardly ever touch in deep storage. is that safe? Does data on drives last forever more or less, especially if you have it on 3 drives?

So on the main external, that still would leave me with about 1.5 TB, most of that also I don't use too much, but a little bit more. Documents word, excel, some music, but mostly Tiff, raw, Jpeg photos. So I could buy new 3 TB externals... Or...

With that scenario which machine and configuration based on all that you would you buy?
What would you buy in for yourself if you had to buy today the 27"

So with the fusion, what happens with images that are not on the SSD? You have to copy them initially over to the SSD? If you have a folder of 50GB of images you know you will be working on, and you want to SSD speed bump. You copy it over there? See, it gets confusing how it works. Isn't just better then to buy the 500 SSD, and in that way the images open faster as they don't have to be grabbed from an external? Is Fusion that good?

Oreo, recommended just getting 500SSD, but I wanted to check, so many people say Fusion.

BTW in the store, the Apple rep says if you order 500 SSD that is your mac HD, that's it, you don't have the other drive of 1TB, also confusing.

Yeah, he kept saying that the OS, which is the most important thing for me to think of space wise, apps, os is 4GB, but on my laptop which I only put 15 GB of my stuff, it's full! and it's a 60 GB hard drive. Why would he keep insisting, the OS is 4GB don't get it...

[reader50]

As the user, you won't see the SSD and HDD. You'll only see the final volume "Macintosh HD". It will have a size equal to the SSD + HDD put together. ie - if you chose the 3 TB fusion (with 120 SSD), Macintosh HD would have 3.12 TB of space.

OSX will attend to the details of what is stored where. Files you use more often will get moved to the SSD side. Again, you won't see this at all. OSX will do it silently in the background. I broke out what is installed in each bay for informative purposes - you were having trouble picturing what a fusion drive is. In practice, you'll see only one Macintosh HD.

About the OS size. The basic OS files take up about 5 GB. Once OSX starts running, it will reserve one or more cache files on disk. Probably reserving about as much space as the RAM you have installed. ie - if you buy an iMac with 16 GB RAM, OSX will reserve at least 16 GB of cache space on your drive. Then you add your personal files.

Base OS: 5 GB
Memory Cache: 16 GB
Personal Files: 10 GB

Whoops, now you are using 31 GB.

The App store may download updates (like the next OS X version) to have on hand for whenever you want to use them. There's another few GB taken up.

Every application you use can potentially use some working space on the drive, and they may not delete their caches when they quit. So it's very common for a working OS install to reach 40 GB.

[kevs]

Thanks Reader great info.

So on a fusion, you don't drag what you want over to the SSD? Finally clarity there. You just open your photos in Photoshop ....

Do you think you would notice a big speed bump if you had the Mac HD only SSD and put you favorite folders on it, knowing 100% it's all SSD? I would never know this unless I had a Fusion and a pure SSD to play around with and compare which I wont have. I want to buy this in the next day or two.

And because I don't, I'm still flipping a coin whether to buy Fusion or pure SSD. It would seem that pure SSD is better as you put a few select folders there with big images and it's 100% all SSD guaranteed huge performance bump, whereas that first time you open those 100mb files on a fusion, maybe they open much slower. But who knows, maybe it's negligible bump — I'm in the dark.

PS-- I do find the Cache in my users library and it's about 1-3 gigs, I delete that but still I see : System at 8GB, rest of Library at 7 GB (not cache), Containers at 3GB, whatever that is....

[reader50]

Originally Posted by kevs 

So on a fusion, you don't drag what you want over to the SSD? Finally clarity there. You just open your photos in Photoshop ....

Exactly. Just open and save your files as normal. Let the OS worry about optimum use of the SSD.

A pure SSD setup will always be super fast. The Fusion will almost always be super fast.

About that 100 MB file. Modern hard drives (especially the bigger ones) can have transfer speeds above 200 MB per second. So even if the file were on the HDD side, it would still open within 1/2 second. The first time.

The system cache files would be under /private (a hidden folder). Like /private/var/vm/

[kevs]

Thanks, so seems you might lean towards buying a 3 TB fustion Mac HD over a 500 SDD? I've had always in the past accessed all my data -- photos, document etc from an external drive, and just leaving the Mac HD for the OS.

Having the data in the Mac HD, even if it's on the traditional non SSD side is way better correct because its not going through cable?

[reader50]

I prefer to store all my data internally because it's quieter and neater. SSDs are totally silent. HDs somewhat less so. External enclosures let some noise out. The iMac case does a much better job of hushing an internal drive. I also have fewer drive icons to choose from, in order to find a particular file.

With Thunderbolt or USB3, there isn't much speed difference today. Your backup drives do need to be external - otherwise anything that destroyed your computer would destroy the backups too.

[Doc HM]

So with Fusion Drve it's not so much about how much data you have but more about how much data you access often.

Since pretty much all photos and music etc spend 99.9% of their lives just sitting on the drive as dead weight then they may as well stay on the spinning part of a fusion drive while OS files, caches etc live on the SSD along with some files that the OS sees you open all the time.

So if you have 300GB of music but listen to a few songs all the time you'll love the speed of the fusion drive.

If you routinely open huge files (ie you 3D render or create video/music) then the fusion drive will feeel more like a normal hard drive.

[kevs]

Thanks Doc, yes, some have suggested going with the 500SSD as the Mac HD, but now I'm leaning to the 3TB Fusion. It would eliminate the need for me to decide what data to put there. I have a good idea of my favorite folders of images (I do photography), and documents, but alas even they are a tad over 400 GB, so I could just put everything on a fusion and not have to think. Also, that eliminates putting my main data on an external as I've always done.

The only downside, is what speed loss you get my not having everything most important always on a dedicated 500SSd, but you don't think that is important?

One other note I might move offsite into the closet about 1TB or images I only open once every few years. If I have 3 copies of that stuff, will it stay there on the archived hardrive indefinitly?

[OreoCookie]

Originally Posted by kevs 

Oreo on this site says definitely get 500 SSD. But I want to spot check. Feel free to jump in Oreo.

I think an SSD-only solution is much more future proof: apart from an old 13" MacBook Pro from 2012 that Apple still sells to special markets, the iMac is the last Mac that doesn't come SSD only. It seems very reasonable that any future optimizations (e. g. a new filesystem or so) will be based on the assumption that you have an SSD. Since you want to keep your machine for a long time, for me the recommendation is clear.

Originally Posted by kevs 

Then another thing just learned is this correct: that the Fusion only works for the OS, not DAta, where if you get pure SSD then you get the benefit of fast start up times (OS,) and also fast loading times for images (date), is that correct? HOPe that made sense.

No, not quite: it is true that OS X will move system files and such on the SSD permanently, and the remaining space is allocated for a large write cache (8 GB, I think) and the rest is reserved for oft-used files. My Fusion Drive uses a 180 GB SSD (I took out the optical drive in my 2010 MacBook Pro and added an SSD), and it seems to be able to use all that space.

However, you should not worry too much about how it works, because it just does. I haven't experienced any failures and it performed as expected: you experience slow downs when you push the system too much (e. g. import > 8 GB of photos or files), when you copy, etc.

Originally Posted by kevs 

Also, please, my OS on my laptop seems to be 45 GB but guy at store says the OS is 4 GB?

That doesn't have to be a contradiction: if you install software they put a lot of files into various system directories (e. g. /Library or /Users/[user name]/Library) which can take up quite some space. E. g. if you have used Garageband in the past, you could have downloaded some of their sample files which eat up several gigs. Also print and scan drivers which have been downloaded on demand and cache files can accumulate. So the claim that OS X takes up 4 GB does not have to be contradictory to the system directories taking up 45 GB, 64 GB is simply not enough for running an OS X machine.

Originally Posted by kevs 

Finally: the imca 27 only comes with 8 GB, 2 4's -- they charge $200 if you want 2 8 instead. Crucial sells 16 for only $35, but don't get how many stickes, maybe I should call them..

When you buy third-party RAM, you have to be sure you pick the right kind, so if you want us to be able to check whether the modules you found are compatible, you need to post a link. If you buy at Other World Computing you can easily pick the right RAM for your machine, their 16 GB kit for the 2015 5K Retina iMac costs $100, a 32 GB kit costs twice that. I would recommend 16 GB initially, you can upgrade that later if you need to.

[OreoCookie]

Originally Posted by kevs 

My Main external is 3TB, with backups up to another 3TB clone, and I have a 3rd 3TB clone off site. This is full about 2.5. TB, and 1tb of that are photos that I hardly ever use. These externals are all about 5 years old, so I should replace them. Maybe I could put that 1TB of photos I hardly ever touch in deep storage. is that safe? Does data on drives last forever more or less, especially if you have it on 3 drives?

So on the main external, that still would leave me with about 1.5 TB, most of that also I don't use too much, but a little bit more. Documents word, excel, some music, but mostly Tiff, raw, Jpeg photos. So I could buy new 3 TB externals... Or...

If your 3 TB drive is 83 % full, you should look at larger capacity drives (I'd multiply your current data by 2, so 5~6 TB).

Originally Posted by kevs 

So with the fusion, what happens with images that are not on the SSD? You have to copy them initially over to the SSD? If you have a folder of 50GB of images you know you will be working on, and you want to SSD speed bump. You copy it over there? See, it gets confusing how it works. Isn't just better then to buy the 500 SSD, and in that way the images open faster as they don't have to be grabbed from an external? Is Fusion that good?

You can't influence whether the files are stored on the hard drive or cached on the SSD. That means if you edit a lot of photos (let's say you import 200 photos to Lightroom), then the SSD cache will in all likelihood not be able to hold all photos. That means at a certain point you experience a “slowdown” because then the data has to be grabbed from the hard drive which is much slower than the SSD. Since I do just that, I went SSD-only as soon as I could.

So for light usage, the difference between a Fusion Drive and an SSD is much smaller, and there are use cases when it doesn't matter (e. g. when you watch movies or play music).

[reader50]

SSDs are pricey today, but falling much faster than HDs. Apple's SSD choice for the iMac is 250 or 500 GB. The last iMacs with that size choice (in HDDs) was in 2006. Today's sizes/prices force you to use HDD storage for media files.

If he gets the 500 SSD, he pays more. And should buy a new external media drive, so it costs more still. If he gets a Fusion, he saves money and gets a new 3TB drive in the bargain. His old 3TB external becomes a 2nd backup. In 3-4 years, he can upgrade to a 4 TB SSD for the same price as that 500 GB SSD today.

[kevs]

Thanks Oreo, Just did PM, you'll see there, this is helping absorbing...

I want a total of 16 ram correct? Apple 27" giveS 8 and then just add 8? Crucial is ok right? I think they are less money than OWC?

Now for drives, I'll ask here could do another thread on this but her: about 1 TB of my data, I hardly ever open, old photos... If I buy new hardrives, can I safely just store indefinilty about 1TB of those images in the closet? I'd have hardrive 3 copies, 2 at home and1 offsite. Then I can buy smaller new hardrives 3TB instead of 4TBS. Also whatever that total comes out to be, for Time Machine, you would be 2x or 3x the grand total?

Now if I go all SSD 500, over time, I would be deciding to put this folder on the SSD, then change my mind, copying it back to the normal hardrive and vice versa, but I guess one could get used to that.... You always want 10% empty space correct? So limit there is 450GB?

Thanks Reader, I just gave a similar argument in a PM to Oreo! Mainly about the ease of just having everything on one big 3TB and then one 3TB clone. But again, I've never experience SSD or Fusion... so I'm listening carefully to Oreo who is very pro go SSD....
You land on getting the 3TB fusion for ease of organization? Not having to decide what goes on the SSD and then moving things off it and then back on..?

[OreoCookie]

Originally Posted by kevs 

Crucial is ok right? I think they are less money than OWC?

Crucial sells many kinds of RAM, and not all are compatible with the machine you want to buy. If you pick the right RAM from Crucial, it will fit, but you can't just pick the cheapest 8 GB stick from Crucial and assume it will work. Even if the RAM physically fits into the slow, it still doesn't mean it will be electrically compatible. You have to give us more detail, otherwise we won't be able to help you.

Originally Posted by kevs 

You land on getting the 3TB fusion for ease of organization? Not having to decide what goes on the SSD and then moving things off it and then back on..?

That's the biggest pro for a Fusion Drive. Reader also has a good point about SSD pricing, although I will add that it's not straight-forward to change SSDs in iMacs yourself. You'd probably need to buy a compatible one.

[kevs]

thanks Oreo, I don't do anything myself, except Ram, so if I went the 3TB Fusion route I would just wait the 4-6 years and then do a huge upgrade. For Ram, then I'll just wait till the computer is here and let Crucial do it's detection on the live computer.

[P]

Originally Posted by OreoCookie 

I think an SSD-only solution is much more future proof: apart from an old 13" MacBook Pro from 2012 that Apple still sells to special markets, the iMac is the last Mac that doesn't come SSD only. It seems very reasonable that any future optimizations (e. g. a new filesystem or so) will be based on the assumption that you have an SSD. Since you want to keep your machine for a long time, for me the recommendation is clear.

The mini is also HDD only (Fusion as a BTO), but this is a good point. The world is moving towards SSDs. Did not consider that fact. OTOH, we don't know what is coming file system-wise, so it is hard to weigh that factor.

[P]

Originally Posted by reader50 

SSDs are pricey today, but falling much faster than HDs.

I have gone on about this for some time now, but the short version: The move to 3D NAND means that supply of flash is increasing very fast right now. In fact, prices should be dropping faster - there is evidence that big manufacturers are building up stock trying to keep prices up:

Flash is too fat. A glut of supply means growth is slower and slower • The Register

Prices should not only drop, they should absolutely crash (don't say "flash crash"). Exactly when that happens is not clear, though.

[Mike Wuerthele]

Amazon's got a 1TB 2.5-inch SSD on sale for $200 today.

[OreoCookie]

Originally Posted by P 

The mini is also HDD only (Fusion as a BTO), but this is a good point. The world is moving towards SSDs. Did not consider that fact.

Sorry, I forgot about the Mac mini, you're right. But also that machine hasn't been updated in quite some time.

Originally Posted by P 

OTOH, we don't know what is coming file system-wise, so it is hard to weigh that factor.

That's definitely correct (I could easily get sidetracked by a filesystem rant here). Nevertheless, I think Fusion Drive is definitely a technology on its way out.

[P]

I actually don't. I think that CoreStorage is a great place to add new features, which means that it won't go away, and as long as CoreStorage is around, they will need some sort of spanning feature. Why rip out the one that is already there?

[kevs]

BTW guys, I have not mentioned this, but for the 15 years I'm on Mac, I've never mixed my OS with important data, so even now, my 1TB Mac HD is just the OS. Should I worry about mixing important data and the OS together?

I could continue on my slow 6 1/2 year old 27" to see the next versions, if they have a great deal on SSD, but I'm really hating this machine, the startup times for excel is one minute and PS CC take about 3 minutes sometimes.

[Mike Wuerthele]

Originally Posted by kevs 

BTW guys, I have not mentioned this, but for the 15 years I'm on Mac, I've never mixed my OS with important data, so even now, my 1TB Mac HD is just the OS. Should I worry about mixing important data and the OS together?

No worries. It's easier than ever to back up data, even off-site.

[kevs]

I think Mike the idea was I wanted to that my back clones for OS on their own container, in case the internal fried out..?

[OreoCookie]

Originally Posted by kevs 

I think Mike the idea was I wanted to that my back clones for OS on their own container, in case the internal fried out..?

Separating data from the OS used to make it easier to get back to a working system. This way you could nuke your system hard drive without any fear of losing data. But this is a piece of advice that's been outdated since essentially the introduction of OS X (which includes Migration Assistant). It's also not really safer, because you could equally well lose your data hard drive instead of your systems hard drive.

What protects you are backups. BTW, you should consider using an online backup service such as Backblaze. For $5/month you get unlimited data. The first upload will probably take weeks, but don't worry about that. It'll also backup external hard drives (unless they are your Time Machine volumes or they are network drives).

Originally Posted by P 

I actually don't. I think that CoreStorage is a great place to add new features, which means that it won't go away, and as long as CoreStorage is around, they will need some sort of spanning feature. Why rip out the one that is already there?

I don't think it's a stretch that Apple will add features which are SSD-only, for instance. Of course they don't need to rip out support for Fusion Drive, but Fusion Drive support would be a legacy feature that will not see any future improvements. Of course, there is no guarantee that current SSDs will necessarily be supported either if, for example, the HFS Next relies on a tight integration between the OS and the SSD controller.

[kevs]

Thanks Oreo. I use super duper to one backup HD on site, and another off site, though the off site one is swapped only every few months now. Would you still do the cloud? I bet it's not a bad idea, super redundancy, but one could not boot off the cloud thing...just another back up for data?

[OreoCookie]

Originally Posted by kevs 

Thanks Oreo. I use super duper to one backup HD on site, and another off site, though the off site one is swapped only every few months now. Would you still do the cloud? I bet it's not a bad idea, super redundancy, but one could not boot off the cloud thing...just another back up for data?

Cloning hard drives is not a good backup strategy, especially if used by itself (I gather you are also using Time Machine). Backups tend to be very old, you have to do it manually, and you only have one or two versions of your data. Time Machine, Backblaze and most other backup solutions allow you to restore to different points in time.

Ideally, you should have many different kinds of backups, and with some you can recover faster with others, you can recover more slowly. However, Backblaze will give you much more regular updates (at least hourly), so you could even combine both. They will also send you a drive with the data on it essentially for free (you will have to pay for the drive at cost, but you get reimbursed in full once you return it). Plus, if you have an iOS or Android device, you have access to all of your backed up files from anywhere.

[kevs]

Thanks Oreo, I schedule on super duper once a day, that' pretty regular. I d have TM but I'm going to buy a new hardrive for that. I've been excluding tons of stuff and now will just get the right size. For TM, is it 2x or 3x Data you own?

I will do Backblaze then as well, it covers iphone tool? I guess you have to have your computer and you iphone onnline a lot of the day for updates to occur? Like icloud? If you needed a bootable OS backblaze will work? If the house burned down that would be nice. As is, I would just boot from the real backup hardrive in the house.