A Month with Apple's Fusion Drive
by Anand Lal Shimpi on January 18, 2013 9:30 AM EST- Posted in
- Storage
- SSDs
- SSD Caching
- Mac
- Apple
- Fusion Drive
Meet Fusion Drive
Available as a build-to-order option on both the new Mac mini and the new iMac is Apple’s own take on SSD caching, Fusion Drive. In true Apple fashion there are only two Fusion Drive configurations available: 1TB and 3TB. The 1TB option is only available on the upgraded Mac mini ($799) or any of the iMacs, while the 3TB Fusion Drive is a 27-inch iMac exclusive.
In all of these cases, the Fusion Drive is a combination of a 1TB or 3TB hard drive (2.5” or 3.5”) and a 128GB Samsung PM830 based SSD. In the Mac minis this SSD is a 2.5” drive, while in the iMacs it’s the same custom interface that’s used in the MacBook Air and MacBook Pro with Retina Display. For my testing I used a 1TB Fusion Drive in a 27-inch iMac.
| Fusion Drive Options | |||||||
| Mac mini (2012) | Mac mini (2012) | Mac mini server (2012) | 21.5-inch iMac (2012) | 27-inch iMac (2012) | |||
| Base System Cost | $599 | $799 | $999 | $1299/$1499 | $1799/$1999 | ||
| 1TB Fusion Drive | - | +$250 | - | +$250 | +$250 | ||
| 3TB Fusion Drive | - | - | - | - | +$400 | ||
| Largest Standalone SSD | - |
256GB (+$300) |
2x256GB (+$600) |
- |
768GB (+$1300) |
||
The size of the SSD used in Apple’s Fusion Drive is much larger than what we usually find in a caching setup. Most OEMs ship with 8 - 24GB of NAND, and even then the drives rarely use a good controller. In the case of Apple’s Fusion Drive, Samsung’s PM830 continues to be one of the best combinations of performance and reliability we’ve ever tested. While I would’ve personally picked something like the Link A Media or Intel S3700 controller due to their excellent performance consistency, the PM830 is probably a more proven and/or affordable option for Apple.
Right off the bat Fusion Drive is different than most of the hybrid/caching solutions we’ve seen, but where it really diverges from the norm is in the software component. This isn’t simply Intel’s Smart Response Technology running under an Apple brand, instead we’re looking at virtualized storage courtesy of OS X’s Core Storage. First introduced in Lion, Core Storage is a logical volume manager that allows the OS to treat multiple physical disks as a single volume.
Apple originally used Core Storage to enable full disk encryption in Lion, but its use has been expanded to Fusion Drive in Mountain Lion. The creation of a Fusion Drive is simple. If you have multiple drives you can create a Fusion Drive yourself using some simple Terminal commands. When you buy a Fusion Drive equipped Mac, Apple does everything for you. Subsequent system and backup restores on your Mac with FD will maintain the Fusion Drive facade, even if you’ve purposefully destroyed the array.
Unlike traditional SSD caching architectures, Fusion Drive isn’t actually a cache. Instead, Fusion Drive will move data between the SSD and HDD (and vice versa) depending on access frequency and free space on the drives. The capacity of a single Fusion Drive is actually the sum of its parts. A 1TB Fusion Drive is actually 1TB + 128GB (or 3TB + 128GB for a 3TB FD).
The latest version of Disk Utility will present a Fusion Drive as a single drive, labeled Macintosh HD from the factory. Apple doesn’t attempt to hide the FD underpinnings however, looking at System Report or using a third party utility like iStat Menus you’ll get statistics on both drives:
If you’ll notice, the 128GB SSD is reported as having a 121.33GB capacity. Since OS X 10.6, Apple has reported capacities in base 10 but if you do the math based on the capacity in bytes you’ll get an idea of how much space is set aside as spare area:
| Apple Fusion Drive, SSD Spare Area | |||||
| Total NAND | Exposed Capacity | Spare Area | |||
| Apple Fusion Drive 128GB SSD | 128 GiB | 113 GiB | 15 GiB | ||
Approximately 11.7% of the 128GiB of NAND is set aside as spare area, which is no different than what you get with a 128GiB SSD in a standard Mac, but a bit higher than the usual 6.7% spare area you get with most of these drives. The added spare area will help improve performance consistency, but it’s still a bit shy of what I like to see on Samsung SSDs (~25%).
You can create Boot Camp or other additional partitions on a Fusion Drive, however these partitions will reside on the HDD portion exclusively.
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cjb110 - Saturday, January 19, 2013 - link
Gaming would have been an interesting 'use' case for the Fusion. When your playing you obviously want the fast access of SSD, but unless its your favourite game, it might not get used much and moved to the HDD.Also Games being much larger 'applications' would quickly fill the SSD if the Fusion just had a simple 'If App = On SSD" rule. Reply
klaudyuxxx - Saturday, January 19, 2013 - link
They reinvented the wheel. 128 GB flash + 1-3TB HDD fused into a single volume?! AKA HYBRID SAMSUNG HARD DRIVES ReplyNCM - Saturday, January 19, 2013 - link
You really haven't bothered to read the article, have you? Or perhaps it's a reading comprehension issue. Replynerd1 - Saturday, January 19, 2013 - link
Typical apple - charging $$$$ for non-tech-savy people.It's way better to have a proper SSD (most laptops and desktops now have mSATA port) in terms of both performance and cost. Yes, I know that swapping the HDD of any apple device kills the warranty and most apple customers don't know how to upgrade a single component..... Reply
Andhaka - Monday, January 21, 2013 - link
Nope, swapping the HDD with a SSD does not kill the warranty and many Apple users do that (I have done it on a 4 years old Macbook).But if other people find it better to pay for the Fusion solution (and a good solutions it seems to be) good for them.
Cheers Reply
pichemanu - Saturday, January 19, 2013 - link
Hi Anand,i saw that in order to test a "pure ssd" setup you connected a 830 ssd to the imac over USB 3. As far as i know the best transfer rate over USB 3 is around 250 MB/s and the worst is well... terrible.
Considering the best case scenario for the iMac:
-USB 3 connected SSD would do 250 MB/s
-SATA 3 connected SSD would do 322 MB/s (taken from your article)
The performance would be 6.94 for fusion drive and 10.19 for a "pure SSD". This is an increase from 114% advantage for the "pure SSD" to 147% advantage for the "pure SSD".
If on the other hand your USB connected SSD did not write at max and a SATA 3 connected SSD would (that is 350 for the samsung 830 on an intel Z77 SATA 3 port) that difference would skyrocket.
Did you check that on your particular workload the USB 3 connection was not a bottleneck?
Thank you.
Reply
mutatio - Saturday, January 19, 2013 - link
Thanks, Anand, for the review. It would be interesting to see some comparisons to aftermarket Fusion setups as have been discussed in the comments here. e.g., How does the Fusion arrangement pan out with a 256GB or 512GB SSD on a Mac Mini? If my Mac were not a laptop I'd likely go for a Fusion setup but I'm not willing to take the hit in battery life while running an SSD and HDD (in the optical bay). Replyphilipma1957 - Sunday, January 20, 2013 - link
I have a 2012 quad 2.3 mini using a 512gb ssd and the oem 1tb hdd. It works very well. I used to run this mini with 2x 512gb ssds in raid0. They were in a pegasus r6 case hooked up via t-bolt. I now run this with the 1.5 tb fusion and a tm plus a clone backup in the thunderbolt case. I prefer the setup this way. I have been doing this for a week I have about 480gb on the 1.5tb fusion . It will take me a while but I will put about 1tb on the fusion I will then see how much it slows. Replypichemanu - Saturday, January 19, 2013 - link
A chart illustrating the possible impact of a USB 3 bottleneck on your test:http://tinypic.com/r/34fir7m/6
Suddenly the fusion drive no longer looks that good ;). Reply
mrbreaker101 - Saturday, January 19, 2013 - link
I have a 2011 Macbook Pro with a 128GB Corsair Force 3 SSD and a 500GB hard disk. I decided to run the commands to make a fusion drive and so far, it's working, although the Force 3 isn't running that fast, despite being set to 6Gbps SATA.I'm going to install some new hardware in my iMac next. A 256GB Kingston Hyper X 3K SSD and 2TB hard disk (with thermal sensing cable from OWC, essential for iMac custom hard disk installs).
I'm not entirely sure I want to make a Fusion drive on the iMac as well. My current usage is about 500GB, with most of that being music files. On one hand, I have no need for mp3s using up my precious SSD space, even if I listen to them 1000 times a day. On the other, the simplicity of no longer having to worry about the locations of files is very appealing.
I also wonder, if I do a fresh install of Mountain Lion and then re-import my photos, media, etc, will Fusion Drive work better than by migrating over a Time Machine backup, which may fill the SSD with music, but leave apps on the hard disk? Reply