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I use a MacBook Air as my primary machine, and the 128GB SSD means space is precious. To save about 10 GB, I've been running Parallels with a Windows XP VM off an external USB hard drive, which performs as well in everyday use as running the VM off the internal SSD.
So, I bought a tiny 32GB USB 2.0 flash drive, plugged it into the MacBook Air, formatted it first as ExFAT (which was slow), then as Mac OS Extended (Journaled) (which was also slow), and copied over my VM file, and ran Parallels off it.
My full experience is documented here: http://www.midwesternmac.com/blogs/jeff-geerling/running-windows-xp-vm
Straight file copies are really fast — 30 MB/sec read (solid the whole time), and 10-11 MB/sec write (solid the whole time). But I noticed that once XP started running, the disk access rates were in the low KB ranges.
Are USB flash drives really that poor at random access, or could I possibly be missing something (the format of the flash drive, etc.?)?
Of note, I've tried the following, to no great effect:
- Formatting the drive as either ExFAT or Mac OS Extended (Journaled)
- Unplugging all other USB devices and turning off Bluetooth (which runs on the right-side-port USB bus).
- Plugging in the flash drive either direct in the right side port, or the left side port, or into a USB 2.0 hub
The main question has to do with the bold paragraph above. I KNOW that flash drives don't have modern HDD throughput ratings, but can someone explain why random access seems so poor? Could it be Parallels, or are flash drives really that bad at random access? – geerlingguy – 2012-01-20T15:30:58.653
1Heh I have a Macbook Air too and was planning on doing the same thing... looks like I won't be now. If there's a memory stick that uses the Thunderbolt port, now then we'd be in business. – Matt Frear – 2012-05-23T16:02:25.850
USB FLASH DRIVE ≠ SSD DRIVE -- Now you know! One's for storage, the other's for disk I/O and long life doing it. – Fiasco Labs – 2012-06-04T00:07:15.180
I have the same problem except I had a single virtual drive on the USB stick holding my profile. I hit some serious lags. It must just be the USB stick cannot handle the IO or maybe it can't handle the multitasking. As far as those talking about performance and using throughput as the standard, they are wrong. throughput is not the correct standard for OS type stuff, you want to look at IOPs and multithreading. – None – 2012-12-30T21:01:06.817
2 years later, is there have been any improvement / solution? I am currently facing this issue – None – 2014-05-17T11:20:45.700