

Fusion drive on older Macs? Yes - basil
http://jollyjinx.tumblr.com/post/34638496292/fusion-drive-on-older-macs-yes-since-apple-has

======
smackfu
He has a couple of follow-up posts too:

[http://jollyjinx.tumblr.com/post/34694173142/more-on-byo-
fus...](http://jollyjinx.tumblr.com/post/34694173142/more-on-byo-fusion-drive-
i-wanted-to-know-how)

[http://jollyjinx.tumblr.com/post/34700977027/fusion-drive-
lo...](http://jollyjinx.tumblr.com/post/34700977027/fusion-drive-loose-ends-
as-hinted-in-my-last)

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rauljara
The moment I saw the fusion drive I was hoping I'd be able to get one as an
upgrade to my current mac-book pro (still using a hard drive). But one of the
big selling points was the automatic switching of commonly used files to the
ssd. I couldn't tell from this blog post if the author was able to recreate
that functionality (I'm not very knowledgeable about filesystems), but without
it, a fusion drive seems significantly less awesome.

Just having the OS on the ssd is still a big win, though.

edit -- Poor reading comprehension on my part. The new OS X does automatically
move files to the ssd. Pretty awesome. Now other world computing needs to
start selling them.

~~~
spartango
Apple's fusion drive is not actually a single part; it's a combination of an
mSATA SSD and a standard SATA HDD. The way fusion drive is implemented, both
devices will need to show up with their own SATA interface for it to work.

Seagate does make single 'Hybrid Hard Drive' parts[1]: an HDD plus 8 or 16GB
of flash to improve performance, but you won't see the performance gains that
you would with a 128GB flash fusion setup. The flash cache is managed by the
controller in those cases, so it's difficult to have apps or OS pinned there.

Alternatively, you can take out the DVD drive in your MBP and use an
adaptor[2] to put in a SATA SSD. This would allow you to use Apple's fusion
software. I've used this setup before, but its number one drawback is poor
battery performance. Moving data lazily between HDD and SSD is fine in a
desktop with continuous power, but could draw multiple watts of precious
battery in a laptop. It turns out to be better to go full flash.

[1][http://www.seagate.com/internal-hard-drives/laptop-hard-
driv...](http://www.seagate.com/internal-hard-drives/laptop-hard-
drives/momentus-xt-hybrid/)

[2]<http://www.mcetech.com/optibay/> ($20 copycat on eBay works fine)

~~~
danielvinson
You have to be extremely careful with compatibility with these Optical Bay
adapters and SSDs. I work at an SSD company and these are the #1 cause of
issues in the field for users. While we don't officially support them, we
still make sure we have functionality - which often requires special firmware
customizations that we would not be making otherwise. I would also not expect
any other manufacturers even test these.

What I can recommend though, is to go with either a Sandforce-based drive, any
Samsung drive, or a Vertex 4.

~~~
PanMan
Why? I also have one of these optibay's, and it doesn't contain any active
parts: It's just a piece of metal to make your drive fit in the place of the
CD drive. Why does this cause issues on the SSD's?

~~~
danielvinson
The same reason why putting SSDs in external enclosures is extremely
inconsistent - power. An SSD needs significantly more power at certain times,
depending on the controller. Most of the time, an optical bay does not provide
the necessary amperage.

~~~
veemjeem
I think your facts are a bit off. The "superdrive" in macbooks require
significantly more power than a SSD. When you burn a dvd using the superdrive,
it requires between 40-50W of power. Even the most power hungry SSDs during
heavy sequential write mode use less than 5W of power. If anything, the
optical drive bay needs to provide more power than the HDD side of things.

It's more likely that the ebay-knockoff adapters were poorly made than it
having anything to do with power requirements.

~~~
danielvinson
Oh, that is exactly what I meant - the Optical drive bays are all made very
badly, and intended for HDDs. The motherboard/connection can certainly power
any drive fine, but the replacement bay cannot.

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js2
Just a quick aside: jollyjinx is the author of JollyFastVNC and ScreenRecycler
(among other apps) and apparently knows his way around OS X at a fairly low-
level (i.e. under the hood).

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joejohnson
To be clear, the author hasn't been able to use a Fusion Drive on an older
Mac. He has instead found a way to create something a lot like a fusion drive
by combining a consumer SSD and HD, and getting the OS to treat the
combination as a single volume. Most impressively, he also was able to use the
SSD "first", moving recently used apps and files to this faster drive.

~~~
DHowett
Fusion Drive is just a fancy name for CoreStorage joining two independent
disks with specific parameters.

Those specific parameters can be replicated using CoreStorage to join two
independent disks. How, then, is that not Fusion Drive?

~~~
perishabledave
All the details aren't out yet, so we can't be certain what is or isn't Fusion
Drive. However, the speculation is that Fusion drive is more than merely a
union of two disks, but with an OS level automatic tiering.
([http://arstechnica.com/information-
technology/2012/10/apple-...](http://arstechnica.com/information-
technology/2012/10/apple-fusion-drive-wait-what-how-does-this-work/))

~~~
3JPLW
> with an OS level automatic tiering.

Yes, exactly. And citing the source you provide, "This [OS level automatic
tiering] is almost certainly done using Apple's Core Storage logical volume
manager, introduced in OS X 10.7. As a volume manager, Core Storage has the
chops to weld the two separate drives together into a single entity and handle
the relocation of files between one tier and the other."

So, then, if you can show that you can merge two disks with CoreStorage, and
get it to tier them such that recently used apps and files get moved over to
the SSD... what more details do you need?

See also the promoted comment on that ARS page: "First off, I am 100% certain
this is HFS+ sitting on top of CoreStorage based on comments made to me by by
certain former coworkers who are still at Apple."

~~~
toomuchtodo
So, it's basically Linux's LVM.

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JunkDNA
Anyone know if this would also work with an older laptop where you replace the
optical drive with a HDD and put an SSD in the hard disk bay? That could
breathe some life into my aging late 2008 Macbook 13".

~~~
whalesalad
Yes, see some of the other comments here mentioning the Optibay.

My old-school first-gen Unibody lasted me quite a while thanks to the MCE
Optibay. I installed an SSD in place of the superdrive for the os/apps and a
320GB old school spinning drive for music/photos/etc...

That old Core 2 Duo felt faster than most modern computers purely because IO
was so much faster.

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rbanffy
I remember ZFS had fancy things like readzillas, writezillas, logzillas...
Sadly, I never had an excuse to play with those.

And since the author mentioned ZFS, it's not hard to make another computer
pretend to be a Time Capsule or other Apple-approved way to use Time Machine
for backups. For me, my TM backups are on a Linux box with a BtrFS volume.

~~~
ssmoot
WARNING: Off-topic ZFS blathering just because I like spreading the gospel.
;-)

I don't think I've heard of writezillas.

Not sure the origin, but a Readzilla was just a (rebranding I guess?) STEC
Mach8 100GB SSD used as a read-cache. In fact, the Readzilla name is rarely
used anymore. The technical name if L2ARC, or Level-2-Adapative-Read-Cache
(Level-1 being the system memory ZFS consumes for caching). In operation, this
will almost always be used close to capacity as long as you have that much
data in the disks behind it.

A Logzilla was a STEC Zeus IOPS (18GB). It operated as something similar to a
RDBMS transaction log, aka the "ZFS Intent Log", or ZIL. This is a Write-Back-
Cache. Even if you're only running HDDs the ZIL is still there to ensure
consistency. If you have SSDs to spare, you have the option of moving the ZIL
to those to increase write performance (up to the point you fill up the SSD
anyways, which doesn't really happen in practice, though it's possible).

If you lose an L2ARC device, no worries, it's pure cache. Even if it's your
only L2ARC device, the worst that's going to happen is things slow down
because there's no SSD caching your data anymore. With that in mind, I usually
deploy two SSDs for an L2ARC, in a striped configuration to increase IOPs. If
I lose one, I still have another, just half the IOPs. If I lose both, well,
back to just the performance of my disks, but all my data is safe.

If you lose your ZIL, you've lost your zpool (the whole logical storage
array). This means you must MUST _MUST_ always have at least two drives for
your ZIL, and they should be mirrored so if there's a failure your data is
still safe. Moving the ZIL off to SSD increases performance, and is absolutely
something you should do, but similar to the Fusion Drive (though for entirely
different reasons), the SSD isn't simply a performance booster, you're
actually moving a critical part of your storage system to it. It needs to be
protected.

More Trivias: Since the ZIL is part of the storage, this is why the Sun
Storage clusters had the ZIL inside the JBODs and not on the 1U server heads.
If you failed over from one head to another, you needed to make sure the ZIL
went with the backing disks. The heads did contain the SSDs used for L2ARC
OTOH since cache is cache, after failing over the new "array master" would
just populate it's SSDs as data was read.

~~~
codex
I use MicroMemory 1GB battery backed PCIe cards for my ZILs. They work quite
well.

~~~
ssmoot
That seems like you're really living on the edge. :-)

My typical setup is:

2.5" 15K-RPM HDDs making up the storage array. Generally in 4 or 5 drive,
single parity sets with a spare for every set up to 3 spares (more just seems
silly). I build out the array with 2 to 4 sets generally. The more sets, the
more capacity and performance while keeping your parity stripes a reasonable
size and ensuring a single drive failure doesn't drastically degrade the
performance of the whole array.

So with 300GB drives, that gives me (300GB * (5 - 1 (for parity))) * 2 ==
~2.4TB usable. Then throw on a couple Crucial M4s or Samsung 830s (had very
bad luck with most Sandforce equipment) as striped L2ARC, and another pair as
mirrored ZIL.

Then use a caching RAID controller with a BBU in JBOD mode.

The reason you want 15K-RPM drives is that things like replication and volume
creation/deletion bypass the ZIL and caches, so while most of the time you'll
be able to push ~30K 8K blocks around in either direction sustained with ease,
for the low level administrative things you'll be limited by your disk speed.
Which in the 10 drive (including spares) 2.4TB example above means you'll have
about 1200 IOPs worth of performance you can tap into. If you'd instead used a
three-drive single-parity set with 2TB SATA drives, you'd be storing a lot
more data on each drive, meaning failures would take much longer to recover
from, not to mention the drives themselves would be about half the speed. On
top of that, for the lower level operations you'd be limited to about 1/10th
the IOPs. Which is not fun at all. Especially if you've made the mistake of
attempting to use deduplication. :-(

This is last-generation stuff though. These HDDs offer less storage, and much
less performance for about twice the price of a good 512GB SSD today. Any new
arrays I build will forgo the L2ARC and ZIL, and go full SSD.

This way you can cut out the 4 SSDs used in the example, and instead of 10
drives, have 10 SSDs. Instead of around ~30K 8K IOPs, you'll have access to
120K. Instead of about 15K for writes, you'll have about the same 120K. And
all your lower level administrative tasks will run at the same speed as
everything else.

So you'll end up with about 4X the performance at less than half the price,
and with ~40% more storage as well. So even if you need the array to have a 4
year life-span, you could replace all the SSDs every couple of years, and
continue to expand the performance envelope with whatever the current
generation offers, and still end up paying less. Not to mention drive bays
aren't cheap. So the all-SSD option means a Dell R820 with 16-bays is now an
option whereas before you'd need the 10 drive bays, 4 bays for SSD, and your
mirrored boot devices... you'd be looking at buying a pretty pricey MD1220 in
addition to the server and now you've given up another 2U as well.

For high-performance IT HDDs are all but dead. We've passed a
price/GB/performance milestone where for 98% of use cases, HDDs should only be
considered for archival storage, not operational storage. IMO.

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xnt14
Is there a way to run a Mac on ZFS? (With a ZFS boot volume, too.)

~~~
Osmium
Not the entire boot volume, but close. People have put user directories, etc.
on ZFS drives. Google "MacZFS" for an older version (ZFS v8) or "Zevo
Community Edition" for a more modern version (ZFS v28). There're active
discussion boards for both.

~~~
xnt14
Interesting... Thanks!

------
arn
If the author is reading, can he/she specify what model of Mac was used?

Update: He answered me on twitter: MacPro3,1

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mhd
This really makes me want to try out putting DragonFlyBSD on some machine, as
its swapcache[1] seems to be quite similar to that (and actually uses a proper
FS).

1: <http://leaf.dragonflybsd.org/cgi/web-man?command=swapcache>

~~~
codex
Linux has several similar implementations, as does ZFS with the L2ARC.

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silasb
Can someone explain how this is different than L2ARC with ZFS?

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codex
It's quite like like a combination L2ARC + ZIL. However, the L2ARC isn't
persistent across reboots (otherwise block writes would need to be journalled,
adding complexity) so you don't get the speed benefits until the machine's
uptime gets large. Not the greatest thing for laptops. Also, I believe the
L2ARC is populated from in-memory pages, while it appears the Fusion Drive can
be populated by a daemon process.

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Osmium
I noticed he used a USB drive for this(!) I wonder what the failure tolerance
is like. What happens if I forget to plug in my USB drive on boot?

~~~
stcredzero
That's just for demonstration purposes. You'd want to gat an optical bay
cradle for a MacBook Pro to do this for real.

~~~
Osmium
I was actually thinking about another usage: adding additional "permanent"
storage to my 128 GB MBA via the SD card slot.

There's a Kickstarter project (Nifty Minidrives) that are selling miniSD card
caddies that sit flush with the MBA SD card slot, so you can permanently leave
an micro SD card mounted for some additional storage. In theory, being able to
pool the storage with the (faster) boot drive would be great. In practice it'd
probably be flaky and a bad idea (especially at current SD card capacities).
But something worth thinking about for the future...

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smackfu
I'm a little unclear on this write-up. Is it actually doing the "move
frequently used stuff to the SSD" part? Or is it just a joined volume?

~~~
rbanffy
Read part three

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dsr_
I gave up on bookmarks-as-bookmarks everywhere except my phone. I can keep the
two hundred or so tabs I need open on modern computers, and that plus search
engines and history suggestions takes care of me.

With late-loading tabs now standard in Firefox and Chrome, they're really
close to bookmarks anyway.

~~~
dsr_
Wrong thread. Sorry.

~~~
rauljara
Downvoted your original so that it falls to the bottom of the page. Upvoted
your apology so as not to punish you for an honest mistake. Though I suspect
your 200+ tabs are not entirely unrelated to your confusion.

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pmjordan
I have to say I'm rather skeptical - the author doesn't say anything about
installing the special "late 2012" version of OSX 10.8.2[1] which supposedly
contains the functionality. Moreover, as far as I can tell, he's just combined
the two drives into a JBOD logical volume (with a total size of the combined
drives). So the first 120GB of the volume sit on the SSD, the remainder ends
up on the HDD. There's nothing dynamic about it. None of the "benchmarks" seem
to disprove this at least, although it's hard to tell until we know how a
"real" Fusion Drive behaves.

~~~
DASKAjA
Make sure you also read the other blog posts in his blog. He _proves_ that
those chained disks transfer popular files to the SSD when they're accessed
more often after a while. He is even on it to show that this technology is
file system agnostic and runs even with ZFS, he also found that its block
based rather than file based:
<https://twitter.com/jollyjinx/statuses/263638394721161216>

