RAM Disks do not speed up Visual Studio

 

The limiting factor for Visual Studio is disk IO. I got a tip to speed up Visual Studio from Channel 9 by creating a RAM disk which sounded like a great idea. However, when I ran a thorough set of tests, I found that the performance difference between the Ram disk and the hard disk were not appreciably different. This was a big surprise since RAM is 240,000 times faster than disk (see my previous blog post). But the reason is because Visual Studio and Vista do a lot of caching. So compile times for the same project in RAM disk and on hard disk were pretty similar. I also tested the time it took to search the entire solution for a word, and times to open a solution. There was no discernable difference!

 

If you still want to try it out and create your own RAM disk, you can download a simple RAMDISK.EXE utility to create a RAM disk in just a few minutes. What is a RAM Disk ?  Ramdisk is a virtual drive created in RAM.

 

Performance Analysis

Creating files was an average of 1.5 times faster on the RAM disk. reading files was pretty much the same between the two disks. Copying a file was actually slightly slower on the RAM disk. All three visual studio tests were pretty much the same between the two.

 

What is the downside of a RAM disk?

Running drivers always give the chance of a blue-screen, and I did have one blue screen when I was first setting up the RAMDISK. (My guess is that I chose a non-default RAMDISK size at first. I typed in 200 instead of selecting 256 MB.) So save your stuff before you run the setup.

If your battery falls out or runs out of juice you will loose everything on your RAMDISK, but this rarely happens to my laptop. I always sleep my laptop instead of shutdown, so my data was always there when I woke my laptop up.

 

 

Performance Tests

So how much faster is a RAM disk than a standard 5,400 laptop hard disk? I used a simple utility DiskBench to measure disk performance.  The RAM Disk was 1.5 times faster creating files. But very surprisingly, for all other tests, the RAM disk and the hard disk were pretty much the same.

 

Conclusion

Sorry, a RAM disk isn’t going to help you out much. It doesn’t beat the natural caching of Visual Studio and Vista. Stick to the hard disk. Also, the pain of having to constantly copy a VS solution from the hard disk to the RAM disk means that it is definitely more pain than it is worth. Perhaps moving your temporary IE files folder would be a good application since it creates a lot of files.

 

Raw performance data.

Note R is the Ramdisk and C is the hard disk. During my test I tried various file sizes ranging from 50 MB to 180 MB. I performed file creation, file reading, and file writing tests. I ran one test against my C drive and then one test against my R drive (ram disk). I shut down all other programs that could potentially compete for IO.

Create File	R:	C:
create file 60 MB	272	425		(milliseconds)
create file 60 MB	273	412
create file 60 MB	206	419
average:	250.3	418.7	1.7	times faster
create file 180 MB	978	1345
create file 180 MB	870	1283
create file 180 MB	945	1344
average:	931.0	1324.0	1.4	times faster
	R:	C:
create file 192 MB	1034	1484
create file 192 MB	1002	1427
create file 192 MB	904	1334
average:	980.0	1415.0	1.4	times faster
create overall average:			1.5	times faster
Read File	R:	C:
read file 201 MB	255	272		(milliseconds)
read file 201 MB	269	249
read file 201 MB	268	419
read overall average:	264.0	313.3	1.2	times faster
Copy File	R:	C:
copy 50 MB to same dir	144	143		(milliseconds)
copy 50 MB to same dir	150	119
copy 50 MB to same dir	169	135
copy 50 MB to same dir	118	121
copy 50 MB to same dir	129	125
copy 50 MB to same dir	117	121
copy 50 MB to same dir	138	121
copy overall average:	138	126.4	0.92	times faster (slower)
Visual Studio Test	R:	C:
open solution with 100 files	5	3		(seconds)
	5	6
average:	5	4.5		(pretty much the same)
Find word in VS	R:	C:
	4	4		(seconds)
	5	5
average:	4.5	4.5		(pretty much the same)
Run VS project	R:	C:
	5	6
	7	5
average:	6	5.5		(pretty much the same)