Released June 2012, Model A1278. Intel processor with Turbo Boost, Up to 512 MB DDR5 Video RAM

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Fusion Drive with Same Capacity Drives?

Hi folks!

MacBook Pro 13" Mid 2012 - 2.9 GHz i7

I'm finally turfing my MacBook's optical drive for an SSD. It feels like the stock 500GB , 5400 RPM, SATA/300 drive is really the thing holding my system back from another few years of solid use.

The thing is, SSD prices have come way down, and I'm getting a 500GB SSD. I'm wondering, is there an advantage to rolling a custom Fusion Drive with the HDD and SSD are the same capacity? Is there a performance advantage over Apple's software RAID 1 (given that fusion was designed to work with the two different technologies)?

I'm also open to other creative suggestions besides just having two different basic volumes.

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Here's your systems specs: MacBook Pro 13" 2.9 GHz i7 (Mid-2012)

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First let's review your systems optical drives ability. Here is the OWC Data Doubler spec sheet: Data Doubler for MacBook Pro. What's important here is the systems clocking. It makes no difference who's you get as the limitation is within the system not the adapter.

In your case OWC notes shows it's workable! So you should be OK here.

As to what to do. A dual HDD/SSD of the same size in a Fusion Drive config doesn't make sense. A RAID set of two SSD's would be a better setup.

So if you are planning on keeping the HDD you'll need to keep it as a dual drive setup. Just leave the HD in the orginal bay and put the SSD in the optical drive. Once you prep the SSD go into Startup Disk to alter to boot drive.

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@danj is the BUS speed of the optical drive as fast as that of the primary drive bay? Will the smaller data path on the optical bay cable vs the wider 2012 cable make a different when going to an SSD?

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I just noticed that the OWC install notes say that a 6Gb/s SATA link will work in the main drive bay, but will be unreliable in the optical drive bay, even though the chipset theoretically supports it. This is probably because that bay (perhaps the SATA ribbon in particular) was only designed for the stock 1.5Gb/s DVD-ROM.

Given this, I'll probably just use two drives with extra storage space (transferring my old HDD to the optical bay).

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@mayer - SATA is SATA, there is no difference between the HD and Optical drive cables as far as SATA signaling. Don't forget the HD cables connection is also supporting the sleep LED & IR sensor which adds the width. The length of the cable only means it will need a bit more shielding and it also puts it at risk of damage (more surface area to get hurt). Frankly, I haven't needed to replace may optical drive cables. Remember we don't do dual drive setups due to the SATA speed issue and needing to be standardized. At this point we are now salvaging parts keeping as many systems running as we transition to gasp! HP laptops.

Technically, the PCH SATA interface defines the SATA port speed. If the HD port is SATA II (3.0 Gb/s) then the optical bays port speed is the same (unless it's PATA).

Now the rub! With the SATA III (6.0 Gb/s) systems the optical drives SATA speed was not reliably SATA III ! This was do to the PCH's timing as Apple pushed the clocking on some systems to an odd division so the PCH did not interface cleanly with the drive in the optical drive caddy (HDD or SSD) at SATA III. This is where you need a FIXED SATA II (3.0 Gb/s) drive (one that does not auto sync) to work reliably.

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@geekmansworld - If you switch the drives around you put at risk the HD! Remember, only the HD bay has HD crash guard protection. The other factor here is your current HD's SATA speed is likely SATA III (check the drives specs) so it won't work reliably in this bay (to fast) if the bay can only support SATA II.

As I said you are lucky to have one of the few systems that a SATA III drive will work in the optical bay.

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@geekmansworld - if you are concerned here just get an older fixed SATA II SSD! Surprisingly you can find them on eBay! Often cheaper than the newer ones.

Don't freak out on the fact the speed is slower it's still plenty fast! Most SSD's are unable to max out the full bandwidth of the SATA III port so you'll be fine here with a SATA II drive.

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I don't know if you can software RAID 1 with an SSD and a fusion drive. Even though they are the same capacity, it doesn't mean their sector layout is the same, so RAID1 will either fail or cause problems.

You will not get the same performance on a fusion drive than a real SSD. Fusion drive speed improvements occur after it learns what you use the most, then copies those files to its internal SSD.

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You can't do both, this is a one or the other condition:

You do a Fusion Drive (large HD & smaller SSD) OR You setup a RAID set with two matching drives.

What is important is the SATA ports speeds also need to match as well so depending on the systems PCH timing this may be an issue (SATA II on the optical SATA connection) which may prevent you from doing either! Then you only have a dual discreet drive config as an option.

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