Speed difference between SSD and Fusion?

Discussion in 'iMac' started by stanw, Oct 14, 2015.

  1. stanw macrumors 6502a

    Joined:
    Aug 29, 2007
    #1
    1. How much of a performance difference speed wise is there between an SSD and a Fusion Drive? Is it a significant difference?

    2. What drawbacks besides speed are there with getting a Fusion Drive?

    Thanks!
     
  2. JustMartin macrumors 6502a

    Joined:
    Feb 28, 2012
    Location:
    UK
    #2
    There's a really (really, really) long thread on here somewhere. Might be worth having a bit of a search. To answer your questions briefly. Assuming a 128Gb Fusion:

    1)

    If you keep less than 128Gb on Fusion Drive, then same speed as SSD. Unlikely, I know, in which case it really depends on how much you access the same stuff. Popular blocks (not files, lower down) are kept on the SSD. So, the stuff you use the most gives you SSD speed. Less popular blocks come up at hard disk speed.

    Writes to disk are same speed as SSD for first 4Gb. After that it goes to hard disk. So, if you write less than 4Gb at a time, then same speed as SSD.

    2)

    The main drawback is that the SSD evangelists will be forever telling you off for buying a 'spinner'.
    A fusion drive is only as reliable as a hard disk. If you think hard disks are unreliable, then fusion is a problem. But, hard disks didn't all stop working when solid disks were invented. And backups are a must whatever you choose.
     
  3. stanw thread starter macrumors 6502a

    Joined:
    Aug 29, 2007
    #3
    Thanks for your reply. I will be using the iMac mainly with an external thunderbolt or USB3 drive to do video editing and Photoshop work. All of the programs will be kept on the iMacs and some data files. In this case, it sounds like Fusion might be fine for me?
     
  4. JustMartin macrumors 6502a

    Joined:
    Feb 28, 2012
    Location:
    UK
    #4
    Well, depends on what machine you're getting. On the new 21.5" Macs, the SSD portion of the Fusion is only 24Gb. I would say that's not enough. So, you'd have to upgrade to a 2Tb Fusion or 256Gb SSD and that's about the same price. If the bulk of your stuff is going to be on an external drive anyway, I would say go with pure SSD. If you didn't want external storage, I'd say go with Fusion.
     

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