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Apple's Fusion Drive: Faster Performance in a Simple Consumer-Focused Package
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Sounds like a great setup, and an appealing configuration in relation to a high-def screen.
Ah, gotcha. I assumed it worked on commonly accessed files, using something like superfetch in Win7. That explains why the idea never took off.
Though I'm still wondering how you'd get around the one problem I'm seeing with the fusion drives. I'd want the OS, programs, and games on the SSD, and my movies, music, and project files on the HDD. Is there a way to set what goes where within the OS, or is it determined solely by install order?
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Those "old" drives are the latest tech
Well, relatively old.
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True, though I'd still want the OS on the SSD for a variety of other reasons. For instance, say I do something that eats up a ton of ram, and usually memory resident aspects of the OS are shunted off to the side to make room. On an SSD, the recovery afterwards would be that much quicker. Plus loading up any random feature usually buried deep within the OS would be that much quicker.
...though with 16GB of ram being rather affordable these days, and the latter mentioned really only netting you a couple seconds difference, it really isn't that big of a deal.
Truthfully, I've only read a small bit about hybrid drives, and the admittedly little I've read seems to point towards it being a rather middling solution at best. It's good only if you want a few of the benefits of an SSD, but don't want to spend the extra cash getting a proper one.
That might've been the case for the first generation of drives. I'll give it another look and see if things have improved since then.
First, I meant to say disk cache. I'm not sure what is the deciding factor for Fusion, or if you can influence it in any way, probably not. I would guess that time of last access, access frequency and file type would be among the parameters that can affect the disk type. But, I'm guessing here.
What I've heard about it is that it's a dumb fire type setup that uses the SSD as the front of the drive, and the HDD as the back. There's no real sorting to it other than "first X GB goes here, rest goes here".
Gawww, I'm gonna have to look crap up now, I bet. I was hoping one of you here would tell me and save me effort.
What I've heard about it is that it's a dumb fire type setup that uses the SSD as the front of the drive, and the HDD as the back. There's no real sorting to it other than "first X GB goes here, rest goes here".
Gawww, I'm gonna have to look crap up now, I bet. I was hoping one of you here would tell me and save me effort.
That's 100% against how apple says it works
Well, that is how a regular disk cache works and the only way it can work. Normal HDDs have a small amount of on board nvram between the actual disk and system ram. The hybrid drives that's been mentioned here adds a SSD section (as a L2 cache on a CPU) in addition to the nvram, still working on a block level, since a disk knows nothing about files.
A tiered storage system like Fusion drive can pick storage with more information at hand, since it has a higher level view.
We're getting into a subject I don't know that much about, so expect me to say a few stupid things along the way here.
See, I'm wondering how it determines what goes where, and how I can set it so that what I want on the SSD goes there. According to this article, the SSD is the priority drive. Everything goes go to it first, and it only starts using the HDD when it fills to capacity (with a 4GB buffer/cache always available and empty). So basically there is no direct way to tell it what goes where. That might not be the end of the world though, because when the SSD is filled to cap, it will eventually start shuffling data between it and the HDD. The end result, while mysterious, might end up with it sorting the "heavier" data to the SSD, and the "lighter" data to the back.
It's seem very Applish to me. As in it's hands-off, works as it's supposed to, but if you want absolute control over what goes where, it's better to just use a dual drive setup rather than fusion.
In the way that has been explained over and over in the two hundred posts preceding yours in this thread.
If it's what I think it is, it's not really a new idea, rather a tweak on an existing technology. As far as the hardware goes, it's not actually a "hybrid" drive. What it's doing is combining two drives into one volume, which OSes have been doing for about forever now.
The fancy spectacular new feature is how it handles the SSD and gives it priority (at least as far as I know). Fusion is basically a strong front end with a weaker support option there to give you extra capacity if you need it.
In other words, it's absolutely nothing like a hybrid drive.
The fancy spectacular new feature is how it handles the SSD and gives it priority (at least as far as I know). Fusion is basically a strong front end with a weaker support option there to give you extra capacity if you need it.
In other words, it's absolutely nothing like a hybrid drive.
On the other hand, enterprise level (looking at $500K and higher for entry level) tiered storage systems work like the hybrid drives. They track sector-level accesses and automatically move "hot" sectors to fast storage - without any knowledge of "files".
It's really unfortunate if the OS-level filesystem code is talking to the volume manager. That's a gross violation of the normal storage abstractions.
But, Apple has many times ignored best practices - only to have it bite their customers in the butts.
Keyword is can, the potential for that for a pure cache is zero. I don't know how this works and neither do you. It's all Apple secret sauce. Edit: seems like a lot of enterprise tiering uses chunks larger than a sector, so it would be something in between.
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It should be blatantly obvious that "sector" and "clusters of sectors" are one and the same at the level I was describing.
And it should also be obvious that if Apple's filesystem is telling the volume manager what to do, that the normal hierarchy of storage abstraction is inverted.
It make me feel dirty just to think about it.
If you can find me a hybrid drive with 128gb of flash (or more), i'm all ears.
(I have a momentus XT, see sig)
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and yes, i'm very happy with it. I also have machines at work with SSD and in actual use for what I do the XT is almost as fast. Power button to login in 12 seconds. And half of that is EFI deciding which drive to boot, etc.
Apps load fast, iphoto flicks through a 60gb library (that I can happily store on the drive, as I have plenty of space) without lagging, etc. I'm very happy.
Given the choice between 128-256gb SSD, and the Momentus XT 750, i'm glad I went for the Momentus Hybrid.
And again, my work machine is a 256gb SSD equipped machine. So i'm no stranger to SSD performance.
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Why? Dell's tiering solution uses a 512kb size, or 2-4MB. IBM Easy Tier uses 1GB chunks, it still provides something in between.
You already said this, and as I already said you don't know anything about if this is the case. But as an aside, breaking abstractions isn't necessarily bad if a sensible new alternative is used.
So you agree - "sectors" and "clusters of sectors" are the same thing.
I'll post a link in the morning, but either Tom or Anand had a description of Fusion which said that the OS level software could pin a file to the SSD or the HDD. That's an inversion of abstraction.
Of course it isn't. If you say "sectors" why would it be blatantly obvious that you really mean "clusters of sectors"?
Well, none of them would have access to any official information in this case. But regardless, you would have to know how the framework for the volume manager is used.
512kb typically, but most importantly it's the smallest unit of data written or read from a disk.
What disks have half mebibyte sectors?
It used to be 512 B sectors, but 4096 B sectors are the norm for current AF disks.
Just give up
What disks have half mebibyte sectors?
It used to be 512 B sectors, but 4096 B sectors are the norm for current AF disks.
Just give up
512 bytes, yes.
I'm sorry, did you just leave? The exact size of a sector is irrelevant to your argument which you just left on the floor.
