Win7 Virtual Machine on SDXC or SDHC card via Parallels

Discussion in 'Windows, Linux & Others on the Mac' started by goombamd, Feb 27, 2011.

  1. goombamd macrumors member

    Joined:
    Apr 18, 2010
    #1
    Hi All,

    Wondering what you think:

    Would running a virtual machine off an SDHC or SDXC card be similar to running Windows7 off of a SSD drive?

    As higher capacity options become available, could you run OSX off the SDXC card?

    I think it's an interesting prospect. Has anyone tried it? What kind of speed boost do you see?

    Thanks!
     
  2. TheHoff macrumors 6502

    Joined:
    Oct 22, 2008
    #2
    SD cards are not very fast. I know the fastest CF cards max out at 90 MB/s and they are very expensive high-end cards. I'd suspect most SD cards are slower than that. So even if you did get it to work, it would be slower than your average platter HDD and nowhere close to an SSD.
     
  3. dagamer34 macrumors 65816

    dagamer34

    Joined:
    May 1, 2007
    Location:
    Houston, TX
    #3
    Fastest SD card is from SanDisk, and it runs at 45MB/s, which is pathetically slow for booting from. Avoid.
     
  4. joergweis macrumors newbie

    Joined:
    May 27, 2013
    #4
    SDXC Cards too slow

    Sorry guys I have to be contradictory here. I have a 95MB/sec SDXC card with backtrack linux installed on it and boot time is fine as well as the execution of the graphical desktop. The whole thing works like a charm. So if you are looking for running vm's from SDXC cards give it a try my experience is not as bad. :)
     
  5. Ledgem macrumors 65816

    Ledgem

    Joined:
    Jan 18, 2008
    Location:
    Hawaii, USA
    #5
    As others have said, you can run your virtual machine from the card but it will be fairly slow. Most SD cards are rated based on their maximum transfer speeds, but that metric isn't important to you. If you were saving photos and transferring photos off of the card then it might, but what you should care more about is the random read/write performance.

    So let's give some comparisons. These numbers are hard to come by but it seems like people are talking about SD cards getting anywhere between 100-250 IOPS at best. Compare that with a "true" SSD like a Samsung 840, which is advertised as having read/write numbers around 100 thousand IOPS.

    The SD card represents a nice option to expand storage with no moving parts, but that durability is one among very few benefits. It is definitely not something you should be looking at for performance.
     
  6. BiggAW macrumors 68020

    Joined:
    Jun 19, 2010
    Location:
    Connecticut
    #6
    It would still be a lot faster than a hard drive, and keep the hard drive from bogging down. If you have a real SSD for booting though, that would be the way to go.
     
  7. saturnotaku macrumors 68000

    Joined:
    Mar 4, 2013
    #7
    No it wouldn't. Even a 5400 RPM laptop drive can read and write at about 100 MB/s, which is still faster than the fastest SD card. SD cards aren't just limited by their own specifications but also the bus of the host computer. Most readers on the market operate at USB 2.0 speeds, which bottlenecks to the point of impracticality.
     
  8. BiggAW macrumors 68020

    Joined:
    Jun 19, 2010
    Location:
    Connecticut
    #8
    Your numbers are nice, but they don't represent reality. When you run the host and guest OSes off of the same HDD, the seek times cause the whole thing to bog down to a near standstill. If you're running one off of an SD card, even if it's a lot slower than the HDD by numbers, it will be a lot faster for the user, as they won't be fighting each other on the hard drive.
     
  9. Ledgem macrumors 65816

    Ledgem

    Joined:
    Jan 18, 2008
    Location:
    Hawaii, USA
    #9
    In terms of random read/write performance, 5400 RPM drives have similar benchmark results as the SD cards (90-250 IOPS, although the number depends on the individual drive and the platter density). However if the SD card is already saturated with sending and receiving data then the random read/write performance doesn't matter because the device is already bottlenecked. Don't forget that a virtual machine isn't a single read/write operation at a time, either; it's dealing with many read/write commands from the operating system and any programs that are running off of it.

    Based off of the numbers the performance might not be any worse than a 5400 RPM drive, although I'm still fairly skeptical of that. I'm also not sure how the card's performance would change with extended use and heat buildup. However, what is for certain is that it will not be anywhere near the performance of a SSD, even though they both use flash memory.
     
  10. BiggAW macrumors 68020

    Joined:
    Jun 19, 2010
    Location:
    Connecticut
    #10
    Agreed, not near that of an SSD. However, an SD card and a hard drive, with the VM running off of the SD card would give much higher performance than an HDD with both. It's the seeking back and forth between the VM and the host that absolutely kills performance.
     

Share This Page