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ibook_steve Jan 31, 2013 07:29 PM
Migrating to SSD + spinning drive
Prices on SSDs are starting to finally get very good. I was looking at a deal on the Samsung 840. I want to use the OWC DataDoubler to put the SSD plus my 750 GB spinning drive in my 2010 MBP:

Mount 2.5” HD or SSD in Optical Bay of Apple MacBook, MacBook Pro Unibody, Mac Mini with DataDoubler

Hardware-wise, this isn't a problem for me. My question is with the OS and files. I know the OS (and applications?) should be installed on the SSD. But what would be the best way to migrate from my single drive to 2 drives? I guess I can put the SSD in a case and use Disk Utility or Migration Assistant, but how do you put the OS on one drive and your User folder (with all my stuff) on another? Is just an alias needed?

Surprisingly, with all my experience, I've never done or tried this. Suggestions?

P Feb 1, 2013 04:19 AM
What I did was the following:

* Connect the SSD, but don't install anything. I named mine "Macintosh SSD", the HDD was named "Macintosh HD" as per default.
* Use CarbonCopyCloner to copy the contents of the HDD, but deselect the folder you don't want to copy. The phrasing is weird, but basically, anything you don't recognize should be cloned as it is likely used by the OS. Easiest way to think about it is to clone everything, but remove the user folder.
* Once the cloning is done comes the magic. In the Terminal, I made a symbolic link from your existing folder to where the user folder is supposed to be with the command

ln -s "/Volumes/Macintosh HD/Users/username" "/Volumes/Macintosh SSD/Users/username"

(as usual, replace your volume names with what they actually are, and insert the actual short username instead of "username")

A symbolic link is like an alias except the UNIX underpinnings understand symbolic links but not aliases, and the Mac parts understand both. Note the phrasing on the terminal: Don't use the ~ shortcut, and make sure that you use the full path with /Volumes even for the current user directory (which is also available at /Users/username).

* Reboot from the SSD and verify that all works.

Alternatively, I suppose one could reinstall the OS on the SSD, boot to the HDD, delete the new user folder from the SSD and do the symlinking.
FireWire Feb 1, 2013 09:25 AM
Great! I've been considering to do the same. Is there any part of the user folder which would benefit from being on the SSD, or do we put the entire folder? What about the VM (swap), should that be on the SSD or HDD?

Would it be best to put the user folder on the SSD and symlink only the bigger folers like Music or Downloads?

And what will happen if we restore from a Time Machine backup? Will it knows it was dealing with a symbolic link or it will recreate the folder where it thinks it is? And having the user folder elsewhere won't mess up application installations or something else?
P Feb 1, 2013 10:44 AM
Swap files should absolutely be on the SSD.

I actually keep my home folder on my SSD and only symlink certain directories out (the three Ds - Downloads, Documents, Desktop), but I know a lot of people just like to symlink the entire home folder and be done with it. I also have my music library in the Documents folder (because that library predates not only OS X but also iTunes, and I've never let iTunes organize it into ~/Music as it likes to do) and a significant number of all the files I own are on the desktop. On occasion I have found some folders that I have manually symlinked out to decrease the load on the SSD, but since I got my new bigger SSD, I have not be forced to do so.

Symlinks work just fine with Time Machine - they have to, the default OS X install has a bunch of symlinks like /etc ->/private/etc. Make sure that both the SSD and the HDD are backed up with Time Machine and that should be it.
FireWire Feb 1, 2013 11:02 AM
OK! I ask because I remember seeing on this forum a few years ago that having the swap on a SSD would "destroy" it because of the many read/write operation which would wear it really fast.
P Feb 1, 2013 05:57 PM
In theory that is true, but with modern wear-levelling algorithms and write-amplification being close to 1.0 these days, you will have write insane amounts of data before it starts to fail. If you have a 250 GB drive with each cell having 5000 writes over a lifetime, that means you can write over 1 petabyte of data before the drive starts to fail. In practice, any HDD will have failed long before that.
ibook_steve Apr 12, 2013 01:30 AM
I finally got a Samsung 840! Question about the symbolic linking: I think you're saying that you create the link when you're booted with the HDD, not the SSD. Is that correct? And with the symbolic link to the User folder, does that mean I don't need to change what directory apps like iTunes and iPhoto are pointing to? And that moving files in and out of those user folders will all happen on the HDD? Sweet.

I decided not to use CCC. I just did a clean install of Mountain Lion onto the SSD and I'll manually reinstall apps onto the SSD.

ibook_steve Apr 12, 2013 01:48 AM
OK, I found this great article with more detail on doing this:

How to Create and Use Symlinks on a Mac — Tech News and Analysis

So the symlink lives on the SSD (like a regular alias would), either for the whole Users folder or for individual folders in there (which is what I think I'm going to try doing). This is a really good tip.

OreoCookie Apr 13, 2013 09:58 PM
I've recently switched from a symlinked two-drive setup to a fusion drive setup. I got tired of managing storage manually, and it also got more difficult, because I ran out of space on my SSD and I would have had to use a more granular symlink structure.

Only a few things are a bit slower, e. g. accessing rarely used mailboxes in Mail. But other than that, it's really great.
shifuimam Apr 19, 2013 10:23 AM
You can also actually move your user folder using...something. Isn't it an advanced view of the Users preference pane? If you move your user folder before you do anything with your profile, you'll pretty much be set.
P Apr 19, 2013 10:37 AM
Quote, Originally Posted by shifuimam (Post 4226782)
You can also actually move your user folder using...something. Isn't it an advanced view of the Users preference pane? If you move your user folder before you do anything with your profile, you'll pretty much be set.
You can, but there has been problems with that (certain programs expect the user folder to be in its usual location). Not sure if it's still an issue, but it used to be.

I'd still recommend moving single folders from your home rather than the entire thing.
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