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I own a mid 2010 6,2 MBP and I am considering the upgrade to a SSD. I would probably get a 256GBs SSD and replace my optical drive for the older HDD, so I can have a little more of capacity, as I seldom use CD/DVD anyway (and could use an eternal USB wrapper if that was the case).

I recently changed my HDD and used disk utility to clone the older one to the new one (which I assume copies the exact blocks rather than operating on the "file data" itself, right?). Everything went flawlessly :) But here the new HDD was bigger and I did not have to take much care hence.

Now I want to upgrade from a 750GBs HDD to a 256GBs SSD. I have some doubts on the best approach to achieve so. Initially, it would be easy to remove or backup unwanted files so I would reach something below 256GBs, maybe like 200GBs of used space. But Would eliminating data and resizing the partition be efficient, regarding the way the data is stored on disk?

I mean, OSX using HFS is somewhat spoken about as not having to perform defragmentation operations, is that REALLY true? If I have 200GBs of the 750GBs on HDD used and resize that partition to, say, 205GBs, for performing the cloning operation to the new SSD, would that be efficient? SSDs perform better on random access writes and reads, but I would like to have my data as continuous as possible, specially if I consider that I will not defragment a SSD, because of the durability issues. :-) If I resized and cloned that older partition, should I worry about data fragmentation or am I just being paranoid?

Furthermore, every once in a while I read people recommending fresh installs. The point is that I HATE wiping my O.S. out for reinstalling it. Hence, my MBP initially had snow leopard, which was updated to lion, which was updated to mountain lion. I NEVER did a fresh install. That concerns me in two ways: Could my data be too much fragmented on the disk, without my knowledge (call me paranoid..)? Furthermore! Am I losing too much performance? For instance, I never achieved those incredibly low boot times that I constantly read people reporting (even with similar specs and almost no login itens or additional kexts loaded). My MBP performs well, it is not as if I NEEDED a fresh install because it is annoying me. However, I am a little perfectionist regarding performance/organization sometimes, I have downloaded installed and removed several applications, libraries, frameworks, they all leave some minor and annoying configuration files and stuff. But I do not know if a fresh install would bring me enough benefits.

Any advice here? :) I know the question is not the most deterministic one, but I appreciate any advices! Thanks in advance.

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There is no concept of fragmentation on SSDs. It only exists on HDDs as data is located at different places physically. –  duci9y Sep 29 '12 at 16:38
    
But why benchmarks talk about sequential data read/write speeds then? I thought that too, but after spending some time reading some reviews, they all speak about sequential read/write operation speeds o.O –  Fernando Sep 29 '12 at 18:26
    
I’m sorry, but that escapes me. Years ago, I was looking forward to defragmenting my 2 GB USB drive. I looked up how to do it and I found that there is no concept of fragmentation in flash memory. –  duci9y Sep 30 '12 at 5:55
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1 Answer

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I'd advise just keeping things simple and clone it over if you can easily get your data down to the smaller size, otherwise do a new install and use Migration Assistant (not for any supposed performance benefits, just that it's simpler).

Fragmentation is not an issue with SSDs because the physical location of the data doesn't change the performance characteristics—each block has the same access time as any other, unlike a hard drive where it takes time to reposition the read/write head over the proper sectors.

In my experience the fresh install thing tends to be more of a Windows thing (and an older Windows thing at that). If you're experiencing specific performance issues, the consider a clean reinstall. But otherwise just clone or use Migration Assistant and enjoy the speed of a new SSD.

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