Delta Engine Blog

This week I wanted to test using a Ramdisk (Ramdrive using just your main RAM) for compiling Visual Studio projects. Playing games or doing other disk intensive stuff would be great too, but most games are just way too big and smaller older games load pretty quick anyway.

While copying files and benchmarking a Ramdisk is incredibly fast with 4-6 GB/s (theoretically my ram should almost reach 10 GB/s, but well that's already way fast enough). Since I use Windows 7 RC since Friday when it came out on MSDN I had a lot of problems finding Ramdisk programs that actually work and do not crash every 2 seconds. Currently I use RamdiskVE by Cenatek, but the company does not exist anymore because it was bought by Dataram, which provides RamDisk on their own now. I was however unable to run Dataram's Ramdisk on Windows 7, it constantly crashes and has also many other limitations. Here is also a discussion on the Ocz Forum about Ramdisks if you want to check out some of the products for yourself.

The Ramdisk is also useful for Temp files, IE Temp files and other Scratch Disk functionality (e.g. Photoshop), but you should only use those for programs to stupid to use more of your Ram (e.g. because a program is 32bit and you have way more memory in your 64bit system). It also will increase the lifetime of your hard disks or SSDs in case you write a lot of stuff on your Ramdisk because the Ramdisk will only be loaded once at start up and saved once when shutting down your PC. But you should be aware that in case of a crash, you will obviously lose all the changed content on your Ramdisk.

For testing I used my new rig with a i7 920 D0 CPU and 12 GB ram, which I overclocked from 2.66Ghz to ~4.4Ghz. This is pretty fast, for example the For vs Foreach Performance application from the last blog post is twice as fast as my 6600 CPU from last week (all times cut in half basically, which is more than I expected).

I also tested quite a lot of hard disks and SSDs, which was kinda interesting because I learned that it does not matter if you mix totally different hard drives into a Raid 0 as long both are similarly fast. For example I tried using 2 older 160 GB disks in a Raid 0 and was only able to get around 60mb/s, which is slower than a single Raptor hard disk, but putting a new fast Samsung 250 GB and a Raptor 150 GB together into a Raid 0 gave me around 160mb/s. To keep things crazy I also added another Intel x25-M SSD to the one I already had and put them into a Raid 0 too, which is amazingly fast (>450mb/s). For highest speed you should always make sure to Enable Write-Through Cache on the Raid controller (in my case a Intel software raid with the ICH10R controller) AND to enable write caching and finally turn off the Windows write-cache buffer flushing (both can be found in hardware->disk->policies) for your disks. Please note that I do not care about data redundancy since everything I do is saved on a server with a Raid 5 anyway. If one of my Raid 0s would fail it would just be annoying to reinstall everything, but I would not lose any of my work or files.

So lets see how much benefit you actually get from compiling several different projects on a fast PC with those different disk configurations. The compile time is obviously heavily dependent on your CPU speed, but I tried to measure how much the total time changes just by using different disks. The following example shows a full recompile of one of my bigger solutions:

All compiles are full recompiles from scratch (no immediate files yet). For testing the DLR (change set 23173, about 25 MB in 20 C# projects), one of my solutions with 5 C# projects, 1 C++ project (~43 MB) and finally the good old Quake3 v1.32 source code (5 MB of c code). Since I do not compile much C++ at home I was to lazy to test bigger C++ projects, but I would guess most times would just scale and the conclusion would be the same.

4 Tests were executed:

Loading Visual Studio 2008 and opening the each solution (average time),
Compiling the DLR and running the ToyConsole sample. This will generate around 25 MB of files (17 MB of those are .pdb), ~60 files.
Compiling and running my own solution (~43 MB, 5 C# projects, 1 C++ project). Generates ~47 MB (lots of copying, >300 files).
and finally compiling Quake3 (~500 c files).

Most of the tests were done several times, but I stopped all of them with this cool freeware stopwatch called PC Chrono. Keep that in mind, the results will not be very accurate. Each test was done on the following drives:

Good old Raptor Hdd (one of the fastest desktop disks you can get, almost empty for better testing)
Single Ocz Ssd with 150mb/s read/write (remember that I complained about the bad JMicron controller on it way back in February)
Intel X25-M Ssd Raid 0 Array with 450mb/s read, 140mb/s write (nice ^^)
And finally the Ramdisk with 4500mb/s read+write (at least)

Disk/Compile times	Loading VS+solution	Compiling DLR+start ToyConsole	Compile&Run own solution	Quake3 Compile
Good old Raptor Hdd	3.75s	9.01s	2.95s	17.57s
Single Ocz Ssd 150mb/s	2.96s	10.47s	3.24s	22.67s
Intel X25-M Sdd Raid 0 Array	1.26s	7.79s	2.88s	17.53s
Ramdisk with 4500mb/s	1.43s	7.70s	2.51s	15.89s

With this data the following fancy graph was build. It shows that there are some improvements in several areas, but as long as you are not limited by your disk speed or IOs (amount of input/output operations you can do per second), you do not get much benefit from way faster drives (the ram disk is at least 45 times faster than the hard disk I used, but the performance improvement is maybe 10 or 20%):

Since it is so much fun using the Intel SSD Raid 0, I will keep using it. It is also big enough to use for all my programs and games. For example launching Left 4 Dead levels is 2-3 times faster than before. But I will probably not continue to use the Ramdisk for compiling. I can just keep everything on the SSD raid, which will not run out of space as soon as my small Ramdisk. Maybe when I do some file-intensive stuff in the future I will try out the Ramdisk idea again.

For now my advise for getting the fastest Visual Studio experience would be getting the fastest CPU you can (i7 920 is pretty nice, overclocking is important too, without it my tests would be 40% slower, 8 hyper-threads might also be useful in the future), enough Ram (4-6 GB), a fast disk like the Intel X25-M and of course using Windows 7 (since everything responses much faster). Then you can really have a lot of fun compiling big and small projects, and playing games, and doing other stuff on your PC.

BTW: My brother also just blogged about Windows 7 RC and using RamdiskVE. He also noticed that the network layer in Windows 7 is way faster than before in Windows Vista for him, in Vista he had 30-60mb/s max, now it is like 110mb/s copying files over the network: