vm on usb 3.0 -- very slow

Discussion in 'Installation and Configuration of Parallels Desktop' started by Ariel Rauch, Jan 5, 2015.

  1. Ariel Rauch

    Ariel Rauch Bit poster

    Messages:
    1
    Hi,
    I just bought a cruzer ultra fit 64GB usb 3.0 stick and moved my VMs to it. Unfortunately it is impossible to work with it as it is very slow.
    I have a MBA mid 2012.

    Any advice?

    Thanks

    Ariel
     
  2. HonzaIl

    HonzaIl Member

    Messages:
    50
    Hello,

    I would first test the speed of the drive (Blackmagic speed test is what I have on my computer). That will tell you how really fast the drive is. SOme are suppose to be fast, but who knows?
    I assume you have it directly in the system, not in some hub? Lot's of hubs are USB2.0 still.
    Here are some numbers of my system:
    Apple SSSD (MBP 2013) 250Mb/s write/450Mb/s read
    Notebook rotational drive in USB3 enclosure - 70Mb/s write / 100Mb/s read
    SD card in card reader on MBP (Transcend JetDrive) 10Mb/s W/85Mb/s R ---> note, that the specs for this card are 60 Mb/s W, 90Mb/s R. Something is slowing this thing down a lot... I tried earlier running off this SD card and it was not very good experience.
    VM from that external drive is visibly slower - I have the VM on the internal SSD :)
    If you get at least 60W/100R Mb/sec (typical rotational drive speed) from the stick, you should be fine. If you get numbers in 20-40s, it will be sloooowww...

    Jan
     
  3. Tom2

    Tom2 Bit poster

    Messages:
    7
    Thanks, Jan.
    Can you explain WHY the drive speed makes so much difference? Presumably the executable code is loaded into memory before being run?
     
  4. HonzaIl

    HonzaIl Member

    Messages:
    50
    Well, VM package contains your "hard drives" - which is your "C:, D:, ... drive" with system, applications, and possibly (bad idea) your data. Note, that the VM drives these are just files in OSX, which look to VM as drives...
    If you need to start system, load applications, read data, ... , these need to be read or written. And speed of reading/writing will impact the speed with which the Windows (VM system) itself will be able to respond. Same as in regular computer - if you have slow drive, it is slow - if you replace it with fast drive (SSD), even slow computer becomes _MUCH_ faster as read/write of data becomes much faster. Actually, old Pentium 4 with enough RAM and SSD is quite usable computer. I tried!

    My VM "hard drive" has ~25Gb, my VM memory allocation is ~3Gb. System in my VM has no chance to cache everything, so it will be reading/writing to my VM "drives" as needed. Faster read/write to these VM drives faster my VM will work.

    In the mean time, I have got one "leftover" older SSD drive and put it in USB3 enclosure. I measured speeds read/write around 220 MB/sec. I moved my VMS there - really fast enough. Tested.

    NOTE: I strongly suggest storing data (as documents, images, music, etc.) on Mac disk where it is backed up by Time Machine or other means, and leave only applications and system in the VM drive. I have seen way too many people here crying, that their VM crashed and now they need to recover some data. System and applications are usually easy to reinstall, but if you loose data, you are toast. You do have backup, do you?
     
  5. Tom2

    Tom2 Bit poster

    Messages:
    7
    Thanks again.
    I agree entirely with the data vs software philosophy, and yes I treat data as valuable (that's my profession.) I back up to a network drive using time machine. Some stuff is backed up to the cloud.
    (I'm trying to figure out a better overall policy for organizing and backing up files.)
     

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