A Month with Apple's Fusion Drive
by Anand Lal Shimpi on January 18, 2013 9:30 AM EST- Posted in
- Storage
- Mac
- SSDs
- Apple
- SSD Caching
- Fusion Drive
Final Words
For the first time since late 2008, I went back to using a machine where a hard drive was a part of my primary storage - and I didn’t hate it. Apple’s Fusion Drive is probably the best hybrid SSD/HDD solution I’ve ever used, and it didn’t take rocket science to get here. All it took was combining a good SSD controller (Samsung’s PM830), with a large amount of NAND (128GB) and some very aggressive/intelligent software (Apple’s Core Storage LVM). Fusion Drive may not be fundamentally new, but it’s certainly the right way to do hybrid storage if you’re going to do it.
It seems that Fusion Drive is really made for the user who doesn't necessarily have a ton of applications/data, but does have a reasonable sized media collection. For that user, Fusion Drive should be a reasonable approximation of a well managed SSD/HDD setup with your big media files going to the HDD and everything that you launch frequently living on the SSD. I’m always going to ask for a larger cache, but I do believe that 128GB is a good size for most client workloads and usage models today. For me in particular I’d probably need a 256GB cache for Fusion Drive to win me over, but I understand that I’m not necessarily the target market here.
The real question is whether or not it’s worth it. I’m personally a much bigger fan of going all solid state and manually segmenting your large media files onto HDD arrays, but perhaps that’s me being set in my ways (or just me being right, not sure which one). Fusion Drive doesn’t do anything to mitigate the likelihood that a hard drive will likely fail sooner than a good SSD, whereas if you go with an internal SSD and external (Thunderbolt or USB 3.0) HDD RAID array you can control your destiny a bit better. Unfortunately, in situations where Fusion Drive is a choice, you don’t often have that flexibility.
On the iMac, Apple limits your options quite a bit. You can either buy a hard drive or the Fusion Drive on the 21.5-inch model, there’s no standalone SSD option. There the choice is a no-brainer. If you’re not going to buy your own SSD and replace the internal HDD with it (or try to see if OWC’s rMBP SSD fits), then the Fusion Drive is absolutely right choice. You’re paying handsomely for the right ($250 for 128GB of NAND is very 2011), but if you’re not willing to crack open the iMac case this is really the only way to go.
For the 27-inch iMac the decision is similarly difficult. Apple does offer a standalone SSD option, but it’s for a 768GB model that will set you back $1300. All of the sudden that $250 Fusion Drive upgrade sounds a lot more reasonable.
On the Mac mini side the decision is far simpler. The Fusion Drive is only available on the $799 configuration (for $250) but so is a 256GB SSD upgrade for $300. As long as you’re ok with using an external hard drive for mass storage, here I’d go for the big standalone SSD. The usual caveat applies: this is only true if you’re not interested in cracking open the mini yourself and using a 3rd party SSD.
To make things simpler, I made bold the options I'd choose given Apple's current lineup in the table below. Note that this is still assuming you're not going down the DIY route (if you do go down that path, buy the biggest SSD you can find and rely on some external mass storage for everything else):
| Fusion Drive Options | |||
| Mac mini (2012) | 21.5-inch iMac (2012) | 27-inch iMac (2012) | |
| Base System Cost | $799 | $1299/$1499 | $1799/$1999 |
| 1TB Fusion Drive | +$250 | +$250 | +$250 |
| 3TB Fusion Drive | - | - | +$400 |
| Largest Standalone SSD |
256GB (+$300) |
- |
768GB (+$1300) |
I am curious to see how long of a roadmap Fusion Drive has ahead of it. Will NAND get cheap/large enough that even the iMac can move to it exclusively? Or will we end up with systems that have more than enough NAND to easily store everything but large media files for even the most demanding of power users? In less than a year Apple could double the size of the NAND used in Fusion Drive at no real change to cost. I suspect another doubling beyond that would be necessary to really make Fusion Drive a one size fits all, but then we're talking ~2 years out at this point and I don't know how static everyone's usage models will remain over that period of time. Go out even further in time, to the post-NAND era and there are some really revolutionary things that can happen to the memory hierarchy altogether...
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BrooksT - Friday, January 18, 2013 - link
Excellent point and insight.I'm 40+ years old; I still know x86 assembly language and use Ethernet and IP protocol analyzers frequently. I'm fluent in god-knows how many programming languages and build my own desktops. I know perfectly well how to manage storage.
But why would I *want* to? I have a demanding day job in the technology field. I have a couple of hobbies outside of computers and am just generally very, very busy. If I can pay Apple (or anyone) a few hundred bucks to get 90% of the benefit I'd see from spending several hours a year doing this... why in the world would I want to do it myself?
The intersection of people who have the technical knowledge to manage their own SSD/HD setup, people who have the time to do it, and people who have the interest in doing it is *incredibly* tiny. Probably every single one of them is in this thread :)
Death666Angel - Friday, January 18, 2013 - link
I wonder how you organize stuff right now? Even before I had more than one HDD I still had multiple partitions (one for system and one for media at the time), so that I could reinstall windows without having my media touched. And that media partition was segregated into photos, music, movies, documents etc. That is how I organize my files and know where what is located.I don't see any change to my behaviour with an SSD functioning as my system partition and the HDDs functioning as media partitions.
Do people just put everything on the desktop? How do you find anything? I just don't understand this at all.
KitsuneKnight - Friday, January 18, 2013 - link
Do you not have any type of file that's both large, numerous, and demands high performance?I regularly work with Virtual Machines, with each of them usually being around 10 Gb (some being as small as 2, with the largest closer to 60). I have far too many to fit on my machine's SSD, but they're also /far/ faster when run from it.
So what do I have to do? I have to break my nice, clean hierarchy. I have a folder both on my SSD and on my eSATA RAID for them. The ones I'm actively working with the most I keep on the SSD, and the ones I'm not actively using on the HDD. Which means I also have to regularly move the VMs between the disks. This is /far/ from an ideal situation. It means I never know /exactly/ where any given VM is at any given moment.
On the other hand, it sounds like a Fusion Drive set up could handle the situation far better. If I hadn't worked with a VM in a while, there would be an initial slowdown, but eventually the most used parts would be promoted to the SSD (how fast depend on implementation details), resulting in very fast access. Also, since it isn't on a per-file level, the parts of the VM's drive that are rarely/never accessed won't be wasting space on the SSD... potentially allowing me to store more VMs on the SSD at any given moment, resulting in better performance.
So I have potentially better performance over all (either way, I doubt it's too far from a manual set up), zero maintenance overhead of shuffling files around, and not having to destroy my clean hierarchy (symlinks would mean more work for me and potentially more confusion).
VMs aren't the only thing I've done this way. Some apps I virtually never use I've moved over (breaking that hierarchy). I might have to start doing this with more things in the future.
Let me ask you this: Why do you think you'd do a better job managing the data than a computer? It should have no trouble figuring out what files are rarely accessed, and what are constantly accessed... and can move them around easier than you (do you plan on symlinking individual files? what about chunks of files?).
Death666Angel - Friday, January 18, 2013 - link
Since I don't use my computer for any work, I don't have large files I need frequent access to.How many of those VMs do you have? How big is your current SSD?
Adding the ability for FD adds 250 to 400USD which is enough for another 250 to 500GB SSD, would that be enough for all your data?
If you are doing serious work on the PC, I don't understand why you can't justify buying a bigger SSD. It's a business expense, so it's not as expensive as it is for consumers and the time you save will mean a better productivity.
The negatives of this setup in my opinion:
I don't know which physical location my files have, so I cannot easily upgrade one of the drives. I also don't know what happens if one of the drives fail, do I need to replace both and lose all the data? It introduces more complexity to the system which is never good.
Performance may be up for some situations, but it will obviously never rival real SSD speeds. And as Anand showed in this little test, some precious SSD space was wasted on video files. There will be inefficiencies. Though they might get better over time. But then again, so will SSD pricing.
As for your last point: Many OSes still don't use their RAM very well, so I'm not so sure I want to trust them with my SSD space. I do envision a future where there will be 32 to 256GB of high speed NAND on mainboards which will be addressed in a similar fashion to RAM and then people add SSDs/HDDs on top of that.
KitsuneKnight - Friday, January 18, 2013 - link
Currently, 10 VMs, totally approximately 130 GBs. My SSD is only 128 GB. Even if I'd sprung for a 500 GB model (which would have cost closer to $1,000 at the time), I'd have still needed a second HDD to store all my data, most of which would work fine on a traditional rust bucket, as they're not bound by the disk's transfer speed (they're bound by humans... i.e. the playback speed of music/video files).Also, for any data stored on the SSD by the fusion drive, it wouldn't just "rival" SSD speeds, it would /be/ SSD speeds.
I'm also not sure what your comment about RAM is about... Operating Systems do a very good job managing RAM, trying to keep as much of it occupied with something as possible (which includes caching files). There are extreme cases where it's less than ideal, but if you think it'd be a net-win for memory to be manually managed by the user, you're nuts.
If one of the drives fail, you'd just replace that, and then restore from a backup (which should be pretty trivial for any machine running OSX, thanks to TimeMachine's automatic backups)... the same as if a RAID 0 array failed. Same if you want to upgrade one of the drives.
Death666Angel - Friday, January 18, 2013 - link
Oh and btw.: I think this is still a far better product than any Windows SSD caching I've seen. And if you can use it like the 2 people who made the first comments, great. But getting it directly from Apple makes it less appealing with the current options.EnzoFX - Saturday, January 19, 2013 - link
This. No one should want to do this manually. Everyone will have their own thresholds, but that's besides the point.robinthakur - Sunday, January 20, 2013 - link
Lol exactly! When I was a student and had loads of free time, I built my own pcs and overclocked them (Celeron 300a FTW!) but over the years, I really don't have the time anymore to tinker constantly and find myself using Macs increasingly now, booting into Windows whenever I need to use Visual Studio. Yes they are more expensive, but they are very nicely designed and powerful (assuming money is no limiter)mavere - Friday, January 18, 2013 - link
"The proportion of people who can handle manually segregating their files is much, much smaller than most of us realize"I agreed with your post, but it always astounds me that commenters in articles like these need occasional reminders that the real world exists, and no, people don't care about obsessive, esoteric ways to deal with technological minutiae.
WaltFrench - Friday, January 18, 2013 - link
Anybody else getting a bit of déjà vu? I recently saw a rehash of the compiler-vs-assembly (or perhaps, trick-playing to work around compiler-optimization bugs); the early comment was K&P, 1976.Yes, anybody who knows what they're doing, and is willing to spend the time, can hand-tune a machine/storage system, better than a general-purpose algorithm. *I* have the combo SSD + spinner approach in my laptop, but would have saved myself MANY hours of fussing and frustration, had a good Fusion-type solution been available.
It'd be interesting to see how much time Anand thinks a person of his skill and general experience, would take to install, configure and tune a SSD+spinner combo, versus the time he'd save per month from the somewhat better results vis-à-vis a Fusion drive. As a very rough SWAG, I'll guess that the payback for an expert, heavy user is probably around 2–3 years, an up-front sunk cost that won't pay back because it'll be necessary to repeat with a NEW machine before the time.