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In an answer to my question on hardware specs for a new computer the author wrote:

A single HDD is not going to give you fast IO performance.

and suggested that I get

a second hard drive, either a small SSD, or a WD raptor

How does having two hard drives increase the speed of a computer?

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4 Answers

up vote 7 down vote accepted

Because sometimes your computer is performing more than one disk activity at once.

Example: you're loading ___MB of game assets from disk #1 while Windows does its pagefile activity on disk #2.

Another reason for a hybrid "fast small disk + slower bigger cheaper disk" strategy is cost. Ideally, you'd have 5TB of fast solid-state storage and no spinning disks. That's not cost effective unless you're the king of an oil kingdom, but most demanding users can probably afford a $250 80GB Intel SSD to speed up OS and key software applications in addition to the 7200RPM drive they were going to buy anyway.

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so is the 2-drive strategy as simple as: (1) SSD contains operating system + virtual machines + most used applications, (2) large HDD contains pictures, videos, etc. or do you want to split up what your accessing, e.g. SSD contains visual studio application and HDD contains visual studio projects? –  Edward Tanguay Oct 25 '09 at 20:34
    
With an SSD it's blurred, as there's no read-lag, and they're bloody fast, but for relatively small things like a VS project it probably doesn't much matter. –  Phoshi Oct 25 '09 at 20:37
    
You probably don't have more than several megs of source code (actual compilable code, not counting assets like images, etc) unless it's an extremely large project. I wouldn't see a need to split up the VS executable and the project onto separate disks - I'd keep them both on the SSD, as Visual Studio's I/O needs are surely not going to surpass what your SSD is capable of providing. –  John Booty Oct 26 '09 at 16:37
    
For a "typical" Windows developer, if there is such a thing, you should be able to fit just about all of your essentials on even a 60GB SSD. On my 60GB SSD I have Win7 Ultimate, Office 2K7, VS2005, VS2008, a 20GB VMWare virtual machine running Win2003, Photoshop CS4, a number of miscellaneous smaller applications, and 5GB of games. And there's still 5GB left over. I was able to do this by moving the paging and hibernate files to a larger drive (8GB saved right there) and using NTFS compression on most of C:\Program Files and C:\Program Files(x86) which saved several GB. –  John Booty Oct 26 '09 at 16:42
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A second physical hard drive will only give you faster I/O throughput when you're copying from one to the other or when otherwise using both disks.

Under most scenarios, where normally you're only using one disk, there is no performance increase.

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Because you can read from two different sources at once.

Your HDD can only read one thing at any one time, and to read another it has to move the read head, two drives can have potentially double the throughput (Two identical drives WILL have double throughput in RAID 0)

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RAID 1 is a mirror, and is not faster than a single drive. RAID 0 is a stripe, and uses both drives as one but also doubling your risk of data loss due to failure. Consider an SSD instead of two drives in RAID 0. –  churnd Oct 25 '09 at 21:42
    
Damnit, I meant 0, thanks for pointing that out. –  Phoshi Oct 25 '09 at 22:34
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The idea is to have your operating system installed on the fast drive (the SSD or the Raptor). Any program files, games, applications you install will be stored here and run from here. You take advantage of a really fast read/write, while not wasting money on space that you won't be using.

Then, you get another drive strictly for storage media. This way you can get a cheap 1TB+ drive. Personally I like the WD Caviar Greens cause they run quiet, cool, and power efficient. This won't effect performance of your computer.

The way I have it set up is I have a 10,000RPM WD raptor for my OS, and I have 2 x 1TB WD Caviar Blacks set up in a RAID 0 to make a 2TB drive, and I back that up with a 2TB external.

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