Apple's New 'Fusion Drive' Not a Typical Hybrid Drive

JesterJJZ said:

What is the procedure when one of the two drives fail? Seems like a Raid0 scenario.

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Sounds like a SPAN/BIG array, with clever software/hardware moving stuff around.

There doesn't seem to be any striping between the two so if one drive fails then the other should be recoverable.

flopticalcube said:

I don't think you understand what the issue is. You have 2 drives now per filesystem rather than 1 so have theoretically doubled the failure rate. This is why Raid 0 drives are considered a more dangerous set up. If the SSD or HDD fails, the data could all be lost depending on how Apple set up the filesystem. It has nothing to do with journaling or backups.

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Raid 0 is dangerous because each file is essentially split between he two drives meaning one disk failing will render your entire system unrecoverable. The fusion drive doesn't seem to be doing this, the file is either on the SSD or the HD so a drive failure should mean the other disk can be recovered.

lilo777 said:

On second thought, it still looks similar to SRT but most likely is not based on one. SRT is a software solution (for a moment I thought it was implemented in a chipset) and it's unlikely that Apple would be even able to use it. Apparently Apple developed similar (software based) solution.

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Nah, SRT works at the disk level. Based on Phil's descriptions, Fusion drive seems to be file system level. Different technology altogether even though their goals may be similar.

Jbod ???

Best new Mac feature Apple has come out with in a long time. Stuff like Power Nap isn't terribly significant, but Fusion is.

It's nice how writes happen to the SSD, then are moved to the HD later. Looks like a good implementation. Too bad we're most likely stuck with sucky HFS+ if we want to use Fusion. For me, data integrity trumps speed, so I'll stick with my dual partition HFS+ / ZFS solution for now.

flopticalcube said:

I don't think you understand what the issue is. You have 2 drives now per filesystem rather than 1 so have theoretically doubled the failure rate. This is why Raid 0 drives are considered a more dangerous set up. If the SSD or HDD fails, the data could all be lost depending on how Apple set up the filesystem. It has nothing to do with journaling or backups.

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Yes, the more hardware you have, the more likely one of them will fail.

But it looks like Fusion Drive works at the file system level. A disk failure would have caused a write fail. During copying, the original file in the other disk should still be intact. They won't delete the file until everything is copied over successfully.

Even if one of the disks failed, you just go to your backup. Everything else stays the same.

A RAID setup is much more lower level. Hence once it's messed up, it could be more difficult to recover in-place.

I'm wondering if this "fusion drive" is having any technical/business/licensing connection to the company "Fusion IO" from which the other Steve (Woz) is the chief scientist.

so it is seen in osx as 1.128 tb?

viacavour said:

Nah, SRT works at the disk level. Based on Phil's descriptions, Fusion drive seems to be file system level. Different technology altogether even though their goals may be similar.

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http://www.anandtech.com/show/4329/intel-z68-chipset-smart-response-technology-ssd-caching-review

Make no mistake, this isn't a hardware feature but it's something that Intel is only enabling on Z68. All of the work is done entirely in Intel's RST 10.5 software, which will be made available for all 6-series chipsets but Smart Response Technology is artificially bound to Z68 alone (and some mobile chipsets—HM67, QM67).

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Ironically, Apple used Z68 in the previous iMacs.

flopticalcube said:

http://www.anandtech.com/show/4329/intel-z68-chipset-smart-response-technology-ssd-caching-review



Ironically, Apple used Z68 in the previous iMacs.

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SRT is implemented in Z68 motherboard firmware. Fusion Drive is an OS technology based on how Phil described it. Not the same thing at all. They deal with different level of stuff. Fusion Drive is higher level, hence less risky or damage can be more localized.

flopticalcube said:

I don't think you understand what the issue is. You have 2 drives now per filesystem rather than 1 so have theoretically doubled the failure rate. This is why Raid 0 drives are considered a more dangerous set up. If the SSD or HDD fails, the data could all be lost depending on how Apple set up the filesystem. It has nothing to do with journaling or backups.

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Raid 0 stripes the data between two drives, so loss of one would make the information on the other useless. In this case, files on the one drive that remains should be intact; this setup would be more sophisticated than lvm in linux, for instance. However, the basic point is that one ought to treat this as a single drive. If a hard drive fails, you get it replaced and pull from your backup. Its the same issue you'd run into with a OS drive and a data drive, essentially. Rescue what you can, then reinstall.

I basically do this already without software on my MBP. I have a 120GB SSD drive as my boot drive with my applications, and a 500GB 7200 RPM drive in place of the optical drive. My machine boots in about 13 seconds, and applications open super fast. I even store most of the files I am currently working on on the SSD drive. It really is great.

xVeinx said:

Raid 0 stripes the data between two drives, so loss of one would make the information on the other useless. In this case, files on the one drive that remains should be intact; this setup would be more sophisticated than lvm in linux, for instance. However, the basic point is that one ought to treat this as a single drive. If a hard drive fails, you get it replaced and pull from your backup. Its the same issue you'd run into with a OS drive and a data drive, essentially. Rescue what you can, then reinstall.

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Yes but multiple drives increase the probability of failure. With Fusion, if 1 drive fails the machine is likely to be rendered useless (depending on where the files have ended up) until the drive is repaired which on an iMac means a trip to Apple.

Daringescape said:

I basically do this already without software on my MBP. I have a 120GB SSD drive as my boot drive with my applications, and a 500GB 7200 RPM drive in place of the optical drive. My machine boots in about 13 seconds, and applications open super fast. I even store most of the files I am currently working on on the SSD drive. It really is great.

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Pretty much. Except that OSX does this for you behind the scene. I want the same thing for my MBA though.

petsounds said:

Fusion Drive is the first "wow" moment I've had during an Apple PR event in a long time, probably not since the original iPhone launch (when it was more like one hour-long wow). It shows they are still doing some innovation beyond "making it lighter and thinner".

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But is this really innovation or repackaging, which is what Apple does the best? For example, I have had a "Fusion drive" in my 2012 Mac Mini for months now. I added in a 128gb SSD, which I use as my boot drive plus applications and use the existing drive for media. Is it innovation for Apple to do what customers have already been doing for over a year? The only thing different is that the Fusion drive is seen as 1 solidity drive, rather than 2, making it more user friendly (again, what Apple does the best).

ECUpirate44 said:

Love the technology, hate the "Fusion" logo.

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Samsung calls it ExpressCache. Sony may use another name and so on. Apple innovates once more with a cooler term for the same old tech.

flopticalcube said:

Yes but multiple drives increase the probability of failure. With Fusion, if 1 drive fails the machine is likely to be rendered useless (depending on where the files have ended up) until the drive is repaired which on an iMac means a trip to Apple.

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Nope. If the boot volume does, the machine needs to be reinstalled. If the data part dies, you just lose whatever files was damaged.

Without Fusion drive, the user would have same failure rate for his regular HDD like everyone else. With Fusion drive, the other "disk" is SSD. There's no mechanical movement, should have lower failure rate compared to a moving disk.

Stetrain said:

In a drive failure with fusion it seems like you would be left with a functioning drive containing the files that were on it at the time of failure.

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It depends a lot on implementation details. While the data on the remaining drive being present would be technically true regardless, practically speaking it might no longer be accessible because all the filesystem metadata describing it might depend on both disks.

viacavour said:

Nope. If the boot volume does, the machine needs to be reinstalled. If the data part dies, you just lose whatever files was damaged.

Without Fusion drive, the user would have same failure rate for his regular HDD like everyone else. With Fusion drive, the other "disk" is SSD. There's no mechanical movement, should have lower failure rate compared to a moving disk.

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SSD's can and do have high failure rates. What if some of the boot files "migrate" to the HDD? Or are some files locked to the SSD?

kas23 said:

But is this really innovation or repackaging, which is what Apple does the best? For example, I have had a "Fusion drive" in my 2012 Mac Mini for months now. I added in a 128gb SSD, which I use as my boot drive plus applications and use the existing drive for media. Is it innovation for Apple to do what customers have already been doing for over a year? The only thing different is that the Fusion drive is seen as 1 solidity drive, rather than 2, making it more user friendly (again, what Apple does the best).

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Of course it is. People have been doing manual work for hundreds and thousands of years before computer was invented. Automating them doesn't mean it's not innovative. In fact, a lot of innovation may go into making things work faster.

ericinboston said:

Apple is so worried about having more than 1 logical and physical drive in all the Macs...as if humans can't remember that drive1 is for the apps/OS while drive2 is for all the data (music, vids, documents, movies, etc.).

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Isn't it that little bit nicer to have everything on a single logical volume?
I'm sure there're people that like having data on both types of drive, but for those people I think it could be improved. For example, finding a file in an open panel only to realize it was on the other volume (yes, you could use Spotlight but if you were doing it on the large hard disk, it'd likely take a while then just finding it manually). Think of it like Exposé - you don't have to remember where which window is.

I wonder when "later" is that the Mac moves imported files from the SSD to the hard drive. One of my biggest pet peeves is sitting down to use Aperture after importing a bunch of new photos, and soon after becoming frustrated by the unresponsiveness of my Mac only to realize the goddamn time machine backup thinks now is a good time to run.

flopticalcube said:

SSD's can and do have high failure rates. What if some of the boot files "migrate" to the HDD? Or are some files locked to the SSD?

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If it's used often, it should stay in SSD. If these system files fail, just reinstall. I have 512Gb of SSD with me, the system files and data are all in the same "disk". By your logic, I have 4 times failure rate than the 128Gb used in Fusion Drive. Haven't have any problem yet.

Apple bought a company that specializes in identifying SSD failure early. That's probably why they are comfortable with incorporating huge amount of SSD and also innovating on SSD so far.

If other companies try to do this without equivalent technologies, then I'd be more worried.

btbeme said:

Way cool technology aside, is anyone else curious how VMWare feels about the name?

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Probably the same way V8 Fusion and a thousand restaurants feel about it.

flopticalcube said:

SSD's can and do have high failure rates. What if some of the boot files "migrate" to the HDD? Or are some files locked to the SSD?

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That's what I was going to reply with on your previous post - I'd assume that system critical files required for booting stay on the SSD (which I'd figure is always the default boot drive). So a failure of the non-boot drive means you can at least fire the machine, connect to a network, access core system applications, etc.

I also wonder if you can flag files for "always on SSD" regardless of their usage history[?]

shanmugam said:

This is actually not needed if apple went with 256GB as standard

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256GB? You can find a 2TB HDD for $80 easily these days, maybe even less.