Fusion drive or HDD RAID 0?

Discussion in 'Mac Pro' started by Taipan, Apr 3, 2014.

  1. Taipan macrumors 6502

    Jun 23, 2003

    On my my 2009 Mac Pro I'm currently using a 256GB SSD (Samsung SSD 830) on a PCIe-SATA-III-Controller for the system volume. The user home folders are moved to a RAID0 array of two 3GB HDD drives (Seagate ST7200.14).

    Now I'm going to replace the SSD with a 512GB model. This makes me wonder whether I should get rid of one of the 3TB HDDs and create a Fusion drive from the other one and the spare 256GB SSD.

    The maximum throughput of the SSD would be bottlenecked by the SATA-II interface, so it would probably be close to the RAID0? So overall the Fusion drive would probably feel faster, wouldn't it?

    What do you think?
    Thanks in advance!


  2. maflynn Moderator


    Staff Member

    May 3, 2009
    With RAID 0 any glitch or issue will cause you to lose all your data across the RAID array. You'd better have a rock solid backup routine.
  3. Chancha macrumors 6502a

    Mar 19, 2014
    Fusion drive is in essence also a form of concatenation, which is no different from RAID0 in the event when one drive fails, the whole logical volume is gone.

    In my opinion in a multi-drive setup like yours I would want more control as to where the files go, fusion is way too automated and transparent. The fastest SSD for OS, the slower SSD for scratch disk, the larger HDDs for data / internal backup or RAIDs.

    Also if I am not wrong, the MacPro logic board has one spare SATA connector unused, you may be able to put one of your 5 drives into the 2nd optical drive bay, and connect it to the SATA port on the board with a short cable, through some holes inside the chassis which were specifically designed for this purpose.
  4. Taipan, Apr 3, 2014
    Last edited: Apr 3, 2014

    Taipan thread starter macrumors 6502

    Jun 23, 2003
    The drive bay is where the old SSD would go. :)

    The number of drives bays is not the problem. But 256GB is too small to hold the whole user folder.
    My thought was that especially reading from the user library folder, which is probably used pretty often, would benefit from the reduced latency of the Fusion drive (as long as the files reside on the SSD part...).
  5. h9826790 macrumors G4


    Apr 3, 2014
    Hong Kong
    The answer is yes.

    I put two 5 years old HDD with 1 new HDD in RAID 0, the old HDD is very slow, just above 60 mb/s, the new one is better, around 120 mb/s. And RAID them together, I get roughly 260 mb/s.

    For the SSD, I connect a Samsung 840 Evo 1T SSD in the 2nd DVD bay via SATA 2, the speed is 250 mb/s.

    So, in my case. I only use 3 HDD and 2 of them a very old HDD. The RAID 0 speed is roughly the same as the SSD in SATA2.

    If you use all 4 bay to RAID some fast new HDDs, you can have around 500 mb/s, which is almost the same as a SATA 3 SSD. However, the data in the SSD will be much more secure.
  6. Chancha macrumors 6502a

    Mar 19, 2014
    I think it is a tough call which only you can decide. Like I said, the major problem of Fusion drive is that you have no control over how it works, or if it is working the way you expect it to. From what you described, you have way more than 256GB worth of data in your home user folder that are deemed "frequently needed". In this case neither Fusion drive or good old manual data management can help them all. But with doing this manually, you have absolute control over what is being put where, which I personally value being important in a multi-drive setup.

    IMO fusion drive was intended for single computer, single drive average users where capacity + fair speed is needed, but he does not know enough about how to manage multiple volumes to utilize the physical advantages of SSDs / HDDs respectively.
  7. Taipan thread starter macrumors 6502

    Jun 23, 2003
    I wouldn't say that there's so much of it frequently needed. My user folder currently has a size of about 900GB, but most of it is in the Movies folder, where it most of the time just sits there.
    What's frequently needed and could probably benefit from fast access is the Library folder, preferences, application support files and things like that.
    You're right, the best thing would probably be to put those on a separate SSD, but I don't feel comfortable with the thought of fragmenting the user folder any further, especially since that would mean creating separate links for every single folder (Movies, Photos, Music etc.).
  8. Chancha macrumors 6502a

    Mar 19, 2014
    I feel your pain, I was once making symlinks after symlinks that even I lost track of where things really were, at that point I decided to get a large SSD for the whole OS X + home folder and that's that...

    In your case fusion driving your entire home folder volume makes sense. If you have enough drives around to prepare for a full switch back in case things go bad, you may as well just try this first to see if the performance is up to expectation. Fusion drive may not be fully utilizing the SSD speed, but in your scenario it definitely can help, and it will be better than having just the HDD.
  9. Gav Mack macrumors 68020

    Gav Mack

    Jun 15, 2008
    Sagittarius A*
    I've had similar issues with clients and myself included with a huge amount of video content and that's to move the video files to their own separate disks and out of the home folder. Having them out means its easier to share for the other user accounts on the Mac, let alone other systems in the house. With most DNLA software like Plex/XBMC you can select additional folders outside of home folders anyway. That frees up your home folder to have one, or even two SSD's running OSX and your slimmer library all on the same superfast media.

    Media drives don't need fast speeds at all so WD Greens are more than good enough, and on a Mac Pro a pair of WD Greens running SW Raid1 will keep each other safe and less of a need to back them up with TM.

    I have nearly 6Tb of video media and getting larger every month :D
  10. Taipan thread starter macrumors 6502

    Jun 23, 2003
    OK, BlackMagic DiskSpeedTest says the speed of my RAID0 is about 300-350MB/s. So the performance hit of the HDD portion of the Fusion drive would be pretty big.
    On the other hand, I just noticed that my SATA-III-Controller has a second port that I can use for the SSD if I route a cable to the optical drive bay. So I can get full SATA-III speed for the SSD.

    Perhaps I'll build a Fusion drive from the SSD AND the RAID0 :).
    ...and start thinking about a double backup strategy :)
  11. m4v3r1ck macrumors 68020


    Nov 2, 2011
    The Netherlands
    Whatever drive config you have, a solid (don't forget the offsite) back-up strategy always rocks! Can't sleep without them... :D
  12. Taipan thread starter macrumors 6502

    Jun 23, 2003
    I have (almost) decided to put the home folder on the SSD and leave the media and data folders on the RAID, though if I'm not too fond of creating multiple symlinks.
    Perhaps I might even (sometime later) get rid of the RAID, since the media files are not performance critical.

    Thanks for your input!
  13. Taipan, Apr 7, 2014
    Last edited: Apr 7, 2014

    Taipan thread starter macrumors 6502

    Jun 23, 2003
    Sorry to bother you again, but I have a loosely related question:

    I have now moved the user home folder to the SSD and the media subfolders to the HDDs, creating symlinks to the original locations. Now the subfolders appear in the home folder with their english names, not the localized ones.

    Is there any way to fix that? Or can symlinks not be localized? I know the localization works via the .localized files, but I don't know where these are supposed to be. Inside the folder to be localized or on the level above?


    OK, found a solution:
    Keep the symlinks with their English names and set the hidden flag to hide them (need the -h option for symlinks). Additionally create Aliases with the localized names.
    Not elegant, but effective. Now the only minor gripe is the generic icons in the sidebar, but I'll get over it.

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