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This question clearly doesn't have one answer, so here are few assumptions:
- I want to add an SSD to my Mac, let's say a MacBook [Pro], with the primary goal of speeding up my workflow.
- The hard disk will stay in the machine, and be mounted as a separate volume.
- the SSD will be too small to hold everything that I need, so I will have to put some stuff away on the secondary hard drive
So the question is: What will be on the SSD, what be be relegated on the hard drive, given this order of priority:
Maximize typical system speed for common operations (boot, launching applications, opening/saving documents).
Maximize space efficiency: use as much of the available SSD storage space for useful stuff (ie speed improvement) without risking running out of space when really needed.
Minimize time spent setting up and tweaking the system
Minimize SSD wear when it makes sense
I classify stuff in three categories:
- A: Stuff that "obviously" need to be on the SSD
- B: Stuff that "obviously" will be on the hard drive, because there is no speed benefit to put it on the SSD, and there is no to little cost to put it on the hard drive.
- C: Grey area stuff: unclear to me, perhaps due to my ignorance/misconceptions.
This question is about the grey area stuff. But before, let's quickly list the other two categories:
A: Stuff that "obviously" need to be on the SSD:
- Mac OS X itself. The OS will benefit a lot from the speed of the SSD. Moreover, most of it is seldom written. So little wear.
- Commonly used applications. For me: mail, development tools, Keynote, a few others
- Home directory: a lot of stuff there will benefit a lot from being on the SSD. Some will fall in the grey area as listed below.
B: Stuff that "obviously" will be on the hard drive:
- iTunes music. More generally, all media files: they are big, and don't need more read speed than real time. This would be different if I edited those media files
- photo database, such as iPhoto databases, unless I do heavy photo editing (which I don't).
- Applications that I don't use very often.
- old documents or projects that are only accessed once in a while
- deep sleep file: while it would help the Mac wake up from deep sleep much faster, I seldom need deep sleep and deep sleep files are rather big
C: grey area:
- OS X swap space: if I really need it a lot, it means I need more RAM. Moreover, thrashing might be less noticeable on a fast, silent SSD than a HD. So I would realize something is wrong later. Finally, should thrashing happen, it would accelerate SSD wear a lot. So put it on the hard disk? But app switching, the best use of swap space, would be much faster on an SSD.
- home directory library folder cache files?
- mail database?
- Spotlight indexing?
- noatime?
- journalling?
- other?
Thanks for any thoughts, especially about swap space.
I recommend you using a hibrid disk, wich have SSD and HDD. Try a seach for Seagate Momentus XT. – Diogo – 2011-06-20T11:47:40.463
I'm not sure how Mac OSX handles hibernation, but I bought my SSD specifically for swap space (in Linux), even though I have way more RAM than I ever use, because Linux uses swap space for hibernation. As a result, waking up from hibernation is now faster than my monitors can react--I can log in before my monitors display the log in prompt, if I'm quick enough. Anyway... you might research how Mac OSX handles that, because the answer may have a big impact on what you put on your SSD. – Flimzy – 2011-06-21T01:33:11.867
Hibernation is called deep sleep. As I mentioned, I don't intend to put the deep sleep file on the SSD, as I almost never use deep sleep. I use regular sleep, where RAM power is maintained by the battery. By default, Mac OS X will only deep sleep when the battery runs out, which is almost never on my MacBook Pro and its 8 hour battery. – jdmuys – 2011-06-22T00:00:51.700
2I disagree with the recommendation for a hybrid disk. At least you haven't supported your recommendation. Tests I have seen show only moderate performance improvements with a hybrid disk relative to a conventional hard disk. This is probably because their Flash memory cache is not really large enough. Finally, this is off topic. – jdmuys – 2011-06-22T00:03:04.117
How would you go about partitioning so that ~/Library is on one disk (SSD) and ~/Music and all the other media type directories are on a different disk? – tladuke – 2011-06-22T19:20:36.053
symlinking is an option, but I had in mind to use iTunes and iPhoto ability to store their media anywhere. – jdmuys – 2011-06-25T12:46:02.633