running VMs off a second HDD?

Discussion in 'Parallels Desktop for Mac' started by jwilker, Apr 17, 2007.

  1. jwilker


    I've got an MCE Optibay in my MBP. 160 Second Volume. I'm wondering if I can run the VMs from there? or do they have to be in library/parallels.

    I search, really I did :) I didn't see it. Figured I'd ask before I tried it so I could avoid maybe asking how to fix something i broke :)

  2. mmischke


    An emphatic 'yes'! Aside from having ample RAM allocated to both host and guest OSs, running a virtual drive image from a separate physical disk is possibly the single most effective thing you can do to boost virtualization performance. Operating systems are constantly reading from and writing to disk, and disk I/O is often a computer's primary performance bottleneck. Disk I/O is roughly 1000x slower than memory access, so OSs spend a lot of time waiting for information to retrieved from the disk. This problem is compounded when you have two OSs competing for access to the same disk. This applies to any virtualization environment, not just Parallels.

    I guess the only possible exception might be if you moved a VM image off of a really fast internal drive and onto a really slow external. It's free to try, though. Just drag the VM to the external drive, repoint Parallels to the new location and give it a shot.

    FWIW, I prefer to avoid external USB drives as it's difficult to get decent sustained throughput w/USB (even 2.0). Firewire's better (that's what I use w/my mini), but nothing beats a second internal tethered off a free SATA bus.
  3. crazibri


    What he said!

    I actually run my VM's on my external firewire drive. Works great and OSX is still very responsive. I wish my external drive wasnt as noisy, but other than that it has great performance.
  4. mmischke


    I hear you about the noise. I went with an external FW 5400 RPM 2.5" PATA drive w/8 MB cache. It's just about inaudible and draws all its power from the FW port. And it's plenty fast.
  5. idanmashaal


    What ever you do, don't get a USB2.0 drive.

    I tried using my VM from my old PC's external Maxtor OneTouch USB2.0 drive (160GB) and the VM is SOOOOO SLOWWW !!
    And OSX, isn't responsive either.

    That's my 0.02$


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