2012 iMac with external fusion drive!

not sure about the rest but if your OS is on the external drive that accidentally get disconnect you need to riconnecet it and restart your computer at it will crash immeditelly!

Once you fuse them the OS will be sitting on the SSD to give you a fast boot, some of the app that you use less frequently will sit on the HDD but not the OS...

You should be able to fuse a partion of your SSD with your internal 1TB drive. Just check the ID of your partion so that you fuse the correct partion with your internal drive.

Somethings are worth waiting for. What you are planing sounds messy, awkward and time consuming. Why?

jDW194 said:

Somethings are worth waiting for. What you are planing sounds messy, awkward and time consuming. Why?

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Not to mention slower as the TB controller will degrade the the speed of the SSD.

Sounds like your planning a disaster. Just order an iMac BTO and wait a few weeks...

MasterLibrarian said:

I finally got my 2012 27" iMac without a fusion drive because I couldn't wait for a bto. I will not stay without one though!

I intend to buy the Seagate GoFlex Thunderbolt adapter and either a Samsung 830/840/840pro or an OCZ Vertex 4 SSD 256GB drive.

My question to those who have fused the internal 1TB with an external SSD:
If I partition my SSD to 2x128 GB partitions can I use the first 128 GB as part of the fusion drive (in combination with the internal 1TB) and keep the second one as a spare drive for my files ? A bit tricky huh?

And in general are you satisfied by the performance of your external fusion drive? What speeds do you get and do you have any issues?

And a silly question: what if the external drive accidentally gets disconnected ?

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I'm not entirely sure you can partition an SSD that you want to put into a FD array before creating the array. I think the initial FD setup is done at the drive level and not at the partition level.

I have done the opposite - I have an internal 240GB SSD that I "fused" with a FW800 external HDD. Total capacity is 2.24TB, and right now I am using 800GB, so plenty on the HDD. When I created the array, ALL partitions on both drives were deleted. You CAN partition the FD array once you create it using Disk Utilities, but from what I understand it will only partition the HDD and not the SSD.

Regarding speed, there are quite a few on here who are using an external SSD as a boot/OS drive connected either via TB or USB3, and they report good speed. It's not as fast as an internal SSD, but it's sure faster than using an internal HDD as a boot/OS drive. My older iMac (2008) is an SATAII internal speed, and I am consistently getting 200MB/s reads/writes when accessing the SSD, and 60MB/s when accessing the external HDD. I say go for it.

If the external drive is disconnected, your Mac will just sit there waiting for it to get connected. It will respond. Once you plug it back in and it mounts, you're back in business.

You can partition either/both of the SSD and hard disk drives to your needs, and then build the Fusion array using the disk/partition ID (disknsn) rather than the whole disk ID. It will work fine.

jDW194 said:

Somethings are worth waiting for. What you are planing sounds messy, awkward and time consuming. Why?

Click to expand...

itsamacthing said:

Sounds like your planning a disaster. Just order an iMac BTO and wait a few weeks...

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This and this.

You are asking for trouble with what you are attempting. Sure, it might work for a long time but there are too many points of failure that could make you wish you had done things right in the first place.

hfg said:

You can partition either/both of the SSD and hard disk drives to your needs, and then build the Fusion array using the disk/partition ID (disknsn) rather than the whole disk ID. It will work fine.

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Thanks for the comment. That's good to know...

Mike in Kansas said:

Thanks for the comment. That's good to know...

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I have some Windows programs I need to use (Quicken, games, etc.) so I always create a bootable Windows partition that I can also use as a Virtual Machine using VMware Fusion or Parallels. I want them on the SSD for speed, as well as OS X, so I partition the SSD (I use larger 256GB or 512GB SSDs) for my Windows partition, and then devote the larger remaining SSD space for OS X Fusion along with the hard disk. I also often partition the hard disk with some Windows NTFS space for game storage, and so do the same thing when I create the Fusion drive using just the partitions I set aside for that purpose.

-howard