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Greg Low (The Bit Bucket: IDisposable)

Ramblings of Greg Low (SQL Server MVP, MCM and Microsoft RD) - SQL Down Under

Need to run SQL Server VPCs faster? -> Fast flash drives do help

Fellow RD and Solid Quality colleague Ken Spencer posted a little while back that he was having good success loading VPC images off flash drives. I thought it was time to try it myself.

The first concept is that not all flash drives are created equal. I went and found fast ones. I ended up with Corsair Flash Voyager GT drives in 16G, which was just big enough to hold the VPC images I was working with. These are extra fast drives that have matched controllers and memory and are rated up to 34 MB/sec. In Australia, they are $119 AUD but I've seen them on US sites for about $63 USD recently.

Next concept is that I needed to reformat the drives as the VPC images were too large for the default FAT32 formatting. As I bought two drives, I tried one with NTFS and a cluster size of 4k and the other also NTFS but with 64k.

The last concept is that these drives are fast for reading but not writing. Virtual PC 2007 seems to insist that the undo disk is in the same folder as the vmc file so I placed the vmc file on my internal eSata 7200rpm 200G drive. That meant the undo disk was there too. 

What can I say? The results show it's worth doing.

Operation Internal Drive 4k Cluster 64k Cluster
Boot To Login 1:27 0:51 0:50
Desktop Appears 2:09 1:07 1:06
SSMS Usable 3:09 1:30 1:28

I haven't done extensive testing of it in use yet but booting twice as fast has to be a good thing :-) The cluster size made only the very slightest difference.

Published Saturday, August 30, 2008 8:57 PM by Greg Low

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Felipe Ferreira said:

hey Greg,

I was thinking to do the same to remove the VPCs from my notebook HD, but I was thinking now...wouldn't be better (faster) to use a external HD case and attach a 500GB SATA II hard drive?

best regards

August 31, 2008 7:14 AM

John Paul Cook said:

I performed extensive test over a year ago and did not find external USB flash memory to be faster. Of course, flash memory is improving quickly, probably faster than Moore's law. I did find that performance testing of Virtual PC is fraught with peril because of caching. I recommend booting the physical machine, do a test, then reboot the physical machine, do another test. Do twoing consecutive tests on the same physical boot can lead to skewed results because of caching. That's the very short summary of 100s of tests.

August 31, 2008 10:21 AM

Greg Low said:

Hi Felipe and John,

I did find much superior performance compared to using an external hard drive. I'm guessing it's simply the lack of seek time.

I'm guessing if you tested it a year ago, you weren't using flash that could do 34 mb/sec. I suspect that's what's changed.



September 1, 2008 1:57 AM

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