Why are people opting for FUSION drives over full SSD on upcoming iMacs?

It's probably only due to cost for the 1tb model.

However, if someone chooses the 3tb model, it's probably because they need more space.

NJRonbo said:

Besides cost -- and maybe it's purely a financial decision -- what do most of you see as the advantage of going Fusion over a full SSD drive?

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1. It's much cheaper
2. You get more storage

There are pretty much no other reasons.

Can't spec for a SSD only option on the high end 21.5 iMac. Can only get the fusion. That's why for me.

It is cheaper, you get more storage space, and there is little to no disadvantage.

Fusion drive is only a way for apple to get decent prices on something that resembles the speeds of an ssd while also getting the size of a hdd. There's no other positive reasons to go fusion. If apple could charge the same for ssd as any other company you could get a ton of ssd for the same price.
Fused ssd disks would have been awesome though. F. Example 3 ssd 512gb ssd disks fused together, each with about 150$ pricetag.but we all know apple would charge 2000$ for something like that

Reasons why I would get a Fusion drive:

1) More storage than a standard SSD

2) SSD speeds with a standard HDD in the chain (yet to be discovered if the speeds remain high when the hdd is over 50% filled)

3) No fuss, no muss. While less expensive or much better storage options if I were to add my own SSD (of larger size), I would then have to access terminal commands, reinstall the OS to my new SSD, etc. With all of the discussions out there explaining how to do this, I could figure it out. But it does seem scary to me as I am not a programmer, and would hate to "brick" my machine without paying for help.

4) Based on the above, while over priced compared to DYI options, it just works.

NJRonbo said:

Blaine,

Confused by that answer. You don't mean 1TB and 3TB SSD. Do SSD drives run that high? I am guessing that is a Fusion Drive combo?

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Meaning that the 768gb ssd is close enough in size to the 1tb fusion, that people probably only choose the fusion because its much cheaper.

MattZani said:

It is cheaper, you get more storage space, and there is little to no disadvantage.

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Little to none disadvantage, well that's a bit of wishful thinking. The disadvantages are huge.
1. All tests so far shows that it has nearly as good performance, but this is only because it has been tested on new machines with empty hdd's. so the ssd is doing all the work. We haven't really seen the fusion tech in the works yet which would obviously slow it down.
2. You have two disks to worry about one regular hdd and one ssd, whichever breaks first will take down the other. So chances of a faulty hdd is suddenly doubled.... So make sure to keep a backup!

The fusion drive concept is simply an extension of the hierarchical storage concept that is already present in the processors. Essentially, there is an inverse relationship between speed and size. This works because locality of reference and temporality of reference is generally pretty high. The hierarchy goes as follows: harddrive, SSD, memory, L3 cache, L2 cache, L1 cache, registers. The harddrive is the largest, slowest, and cheapest. The registers are the smallest, fastest, and most expensive. Just like it is a good economical tradeoff to have levels of cache in the processor, it is a good economical tradeoff to introduce an SSD into the hierarchy. You don't need all data on the SSD because the data you reference most often will "migrate" there just as it does with cache levels in the processor.

NJRonbo said:

Just curious...

I know very little about SSD drives other than the fact that Apple charges a pretty penny for them.

I have a full 512GB SSD drive on my Retina Macbook Pro and I will never go back to a hard drive.

So, when I put together my new 27" iMac, I am looking to get a full SSD drive over a Fusion drive. I put a lot of software on my computer and I want all of it (not just some of it) to launch as quickly as possible.

Looking around at posts on this board, it seems that many are opting for the Fusion drive.

So, here is the question....

Besides cost -- and maybe it's purely a financial decision -- what do most of you see as the advantage of going Fusion over a full SSD drive?

Wouldn't you want the ability to have more SSD space available for all the software you will put on your computer for the next few years?

Perhaps I'm missing out on something due to my lack of knowledge about SSD drives. I have heard something about them slowing down over time when constantly writing/rewriting to them.

Thanks

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4GB is a boatload of software? That sounds like the average install size for one app...

Siderz said:

1. It's much cheaper
2. You get more storage

There are pretty much no other reasons.

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What he said.

The "fusion drive" has an SSD part that is 128 GBs - that is pretty big. Basicly, the OS will fill up the SSD part of the "fusion drive" and then start storing on the "harddrive" part of the "fusion drive". In addition, files that are repeatedly referenced will "migrate" to the SSD part or just stay on the SSD part if they are already there. This happens without you explicitly doing anything other than use the system. This is the idea behind a hierarchy - the files (data) you use most often will tend to stay on the fastest storage (the SSD part). Files (data) that are seldom referenced will "migrate" to slower (and larger) storage (the hardrrive part). Remember that it isn't just the programs (apps) - there are datafiles that the programs reference. This concept is present on large systems and often includes a "robotic tape system" as an additional level in the hierarchy. I like the concept because it is transparent to the user and generally works well. It works well because most users will repeatedly use the same files often (temporality of reference). Hierarchical storage system, such as the fusion drive, are popular because they are much cheaper than providing the equivalent amount of storage constructed entirely with the fastest component (the SSD part) but provide nearly the same performance because of the temporality of reference. This is entirely about "bang for the buck" - essentially you are trying to achieve the best performance for the lowest cost as opposed to the best performance at any price, while also making it transparent to the user.

NJRonbo said:

Tuccillo,

Got a little lost in your tech (but thank you nonetheless).

The question I have, if I plan to put a boatload of software on my computer -- and generally I put close to 4GB worth on my Mac -- won't I benefit with an SSD over a Fusion? I don't think the Fusion has enough room for most of the programs I use to migrate over there.

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Let's see..

1 TB HDD:
Estimated Price: $0 (included)
Capacity Factor: 1
Speed Factor: 1

768GB SSD:
Estimated Price: $1000-1300
Capacity Factor: 0.77
Speed Factor: 4

1 TB Fusion:
Estimated Price: $250
Capacity Factor: 1.13
Speed Factor: 3.5


Fusion appears to be perfectly acceptable compromise for the speed and cost differential.

Mh i would like to know how fast Fusion Drive would Start an App. That has been used rarely

You don' really know the "Speed Factor" for the fusion drive because if depends on where the data is stored. For most users, however, I suspect the "hit rate" on the SSD component will be pretty high - that is why these sorts of things work.

forty2j said:

Let's see..

1 TB HDD:
Estimated Price: $0 (included)
Capacity Factor: 1
Speed Factor: 1

768GB SSD:
Estimated Price: $1000-1300
Capacity Factor: 0.77
Speed Factor: 4

1 TB Fusion:
Estimated Price: $250
Capacity Factor: 1.13
Speed Factor: 3.5


Fusion appears to be perfectly acceptable compromise for the speed and cost differential.

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it's all about price

according to the tech specs on the product page and a conversation with apple sales support the only iMac SSD option is limited to the 768GB

"Configurable to 3TB hard drive, 1TB or 3TB Fusion Drive, or 768GB of flash storage."

price of upgrading to the 768gb from 256gb on the 13" retina is £800 / $1300 so we'd assume similar on the iMac

that's a lot of money to throw at an SSD... at US prices, it's a whole entry level iMac.

It depends. If the App (and data files) are present on the SSD component then it will be faster than if they are present on the hardrive component. Just because the app (and data files ) are rarely used doesn't mean they are not on the SSD component. They could be if initially stored on the SSD component and the space they are taking on the SSD component isn't needed by something else. In other words, if the SSD isn't full then they could still be SSD resident. There are several different replacement strategies for hierarchical systems - I don't know the exact details of the Apple implementation.

L3g4to said:

Mh i would like to know how fast Fusion Drive would Start an App. That has been used rarely

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iamgalactic said:

according to the tech specs on the product page and a conversation with apple sales support the only iMac SSD option is limited to the 768GB

"Configurable to 3TB hard drive, 1TB or 3TB Fusion Drive, or 768GB of flash storage."

price of upgrading to the 768gb from 256gb on the 13" retina is £800 / $1300 so we'd assume similar or on iMac

that's a lot of money to throw at an SSD... at US prices, it's a whole entry level iMac.

Click to expand...

There is the possibility that a BTO option might allow for both the 768GB SSD and the 3TB hard drive ... then the user could join them into a "Fusion" drive if desired. I am sure that will be expensive however.

In these sorts of hierarchies, there is typically a large ratio between adjacent levels. For the advertised fusion options, the ratio is 8 to 1 for the 1 TB harddrive component and 24 to 1 for the 3 TB harddrive component. That is where the cost savings comes from.

hfg said:

There is the possibility that a BTO option might allow for both the 768GB SSD and the 3TB hard drive ... then the user could join them into a "Fusion" drive if desired. I am sure that will be expensive however.

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tuccillo said:

In these sorts of hierarchies, there is typically a large ratio between adjacent levels. For the advertised fusion options, the ratio is 8 to 1 for the 1 TB harddrive component and 24 to 1 for the 3 TB harddrive component. That is where the cost savings comes from.

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I wasn't suggesting this for cost savings, but for single-drive file management convenience for those who want a massive SSD main drive and also have huge photo, music, video libraries. Obviously these could be managed manually, as users who have them are currently doing, but if you want background management the Fusion join would permit this. I imagine the current Fusion choice of 128GB is simply that that is the cheapest most cost-effective way to implement it today. Anything smaller would not be adequate.

This would also give you plenty of space to put your Windows partition on the SSD if desired for speed, which a 128GB wouldn't permit.

tuccillo said:

You don' really know the "Speed Factor" for the fusion drive because if depends on where the data is stored. For most users, however, I suspect the "hit rate" on the SSD component will be pretty high - that is why these sorts of things work.

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Of course. We're talking averages here. If you use more than 128GB of data/apps frequently, then you'll hit a slowdown once in a while when you start up the thing you least recently or least frequently used. I feel like this shouldn't happen too often, though - I don't know exactly how it was designed, but I would think it would make sense to prioritize keeping the apps on the SSD and the data on the HDD, to more easily take advantage of the 4GB write buffer on the SSD. The only time I would expect to see normal HDD speeds is, say, if you want to shuffle your entire video collection around or onto/off of an external.