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I recently purchased a Macbook Pro. I had an SSD from my last computer which I formatted, installed into my Mac, and used as my one and only HD (I don't need that much space so I didn't opt to do the upgrade where people pull out their optical drive).

I'm not much of a hardware guy - my knowledge is limited to basic understanding of where my data is hiding and how to swap parts. I do work in Eclipse though, and I'm noticing that my RAM usage is near 100% (I still have the default 4gb installed).

I'm considering going for the 8gb install, but I'm wondering, Is upgrading the RAM worth it if I have an SSD already? I know that when RAM is full it will use swap space on the hard drive so I don't know if it would benefit me to get an SSD or not...

I know there are some similar questions out there, but they all seem to focus on "Should I get RAM or SSD." I've got the SSD, I just want to know if the RAM would provide any increase in performance.

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Yes. RAM, HD and CPU all serve different purposes. RAM is always a good investment regardless. And considering 8 GB sells for ~$45, a cheap one. –  cksum Mar 24 '12 at 20:48
    
Since you reach near 100% RAM usage it means you will benefit from extra ram for sure . I got an 8gb crucial memory kit from amazon recently for just £30. I believe its a worthwhile upgrade. –  latusaki Mar 25 '12 at 12:39
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5 Answers 5

up vote 12 down vote accepted

RAM still is a lot faster than any SSD which you use in your Mac. RAM has a shorter access times and much higher transfer rates:

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[table]

The SATA interface by which the hard disk is connected limits the throughput to a theoretical maximum of 6Gbit/s (600MB/s) for SATA3.

You can determine how much the page outs are written to the disk by taking a look at the Activity Monitor. I try to keep the ratio at a maximum of 10/1 (page in/page out). The more page outs you have, the more like a RAM upgrade will benefit you.

enter image description here

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Was ist los? Ein Deutchen tisch auf a English forum? –  radarbob Apr 13 '12 at 13:30
    
@radarbob Whenever I can, I'll use English sources. But sometimes I can't find any :) This link will use Google to translate the website. –  gentmatt Apr 13 '12 at 16:58
    
It just struck me that this answer implies one should totally forget about an SSD, max-out memory and create a virtual drive in memory, dump key apps and files in there and go to town. I've done this with some of my older (pre OS X) macs. –  radarbob Feb 13 at 22:19
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On MacPerformance.com look for Optimizing the MacBook Pro Core i7 on the home page. It's a 5 part article that compares combinations of 4/8GB memory with & without an SSD.

Just eye-balling the graphs, and other random experience guessing, I'd say

  • Given 8GB memory, an SSD is absolutely worth while.
  • If you have 4GB memory, upgrade memory first
  • If you have 8GB memory, upgrade to an SSD
  • For Joe Average User, once you have an SSD upgrading beyond 8GB memory is virtually pointless.

Other points specific to recent MPB models

  • Make the SSD the boot drive. (not MPB specific)
  • Get an SSD w/ 6G (speed) interface, vice 3G.
  • The MPB main drive slot has a 6G interface, the CD ROM slot has a 3G interface
  • Don't put a 6G drive in the CD ROM slot. It's buggy. Also a waste of $ of the premium for a 6G SSD. See MacPerformanceGuide.com for more info.
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This is hard to say, without knowing exactly how you use your computer it's difficult to suggest exactly what the outcome will be, but one thing is for sure your performance will not decrease if you throw more RAM in ;)

Having said that, if you had an issue with low RAM, one of the things you can expect to see is more virtual memory paging. If you already have an SSD, then that paging process is likely to be considerably better performing than for an normal HD.

As such it's possible that the SSD is already making up for low RAM by paging much faster. The boost you may get from more RAM will be lower than if you had a spinning magnetic platter.

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It depends what you want to do. Your computer's memory and its storage are used in different situations — and thus performance improvements will affect different aspects of your workflow.

  • Memory (RAM) is used to keep track of data used by currently running applications.

    Upgrading your RAM will improve your ability to work with many applications at the same time, and open/work with large files. Your computer will feel more responsive.

  • Storage (SSD or HDD) is used for long-term file storage, and manipulation of files which don't fit in memory. Also, if your system memory is full, a swapfile is used to extend the memory using your disk.

    Upgrading your HDD to an SSD will make downloads and other file operations faster, and in some cases it may make applications more responsive. It also has the benefit of no moving parts, so your computer will be more robust against sudden motion.

But note: SSDs are still slower than RAM! If you're using more memory than your system has physical RAM, upgrading to an SSD may improve the speed of virtual memory (your swapfile), but you won't see the same improvement as you would if you add more RAM. Plus, the less swapping you do, the less wear you incur on your disk.

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Just to add to this, maxing out your RAM cuts down (almost eliminates) swapping. And thus saves on cell SSD cell wearing, giving it a longer life span. –  cksum Mar 24 '12 at 20:52
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I consider 4GB OK for current general Mac usage. 8GB is better, 16GB is what I currently have (although not "officially" supported in a current MacBook Pro, it works well and OWC sells a kit). You just can't have too much RAM. Right now it is relatively very cheap, compared to what we used to have to pay.

Even if you have a SSD, paging (virtual memory) is still considerably slower than having RAM available. Memory-hungry apps like Photoshop, Xcode and Safari on a system will be noticeably faster on any system where they are able to access all the memory they need rather than having to go to virtual memory. In fact the presence of any two of those apps is more than enough justification for me to install 8GB.

I would rather have the RAM upgrade than the SSD.

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