There are varied opinions on this question, but before we go into that, maybe a short overview on servers and hard drives is in order.

A web server is nothing more than a computer that uses software applications to serve up web pages in response to remote browser requests. And like all computers, it too has a hard drive, a central processing unit and memory, among other things. But because servers handle more than one browser requests at a time, 24/7, reliability is an important issue. Thus, data is typically stored in multiple hard drives through a process known as RAID (Redundant Array of Inexpensive Disks). But what type of hard drive is best for web hosting purposes?

There are three types of hard drives available, based on their interfaces.

• IDE – (or Integrated Drive Electronics) is an interface used between a computer motherboard's data paths or bus and the disk storage devices. It was adopted as a standard by the American National Standards Institute (ANSI) in November 1990 as the Advanced Technology Attachment (ATA).² Here, encoding, decoding and control signals are done on the circuit board under the drive and independent from the computer.

• SCSI – (or Small Computer System Interface, ‘skuzzy’) is an ANSI standard electronic interface, where the bus is separate from the usual buses such as PCI or SCA. SCSI drives are independent and do not rely on the BIOS to talk to the computer so it speeds up processing. It requires a driver that is unique to the operating system you use as well as your special hardware combination so it is harder to configure. The lack of set standards for SCSI also means that one drive may not necessarily be able to talk to another made by a different company.³ Its widely implemented standard is Ultra-2 SCSI for a 16-bit bus (with data transfer = 80MBps and up to 7-15 devices can be connected per SCSI port) and its latest standard, Ultra3 can operate at full clock rate (or 160MBps).⁴

• EIDE – (or Enhanced IDE) is much like the IDE, only, it can use many devices to one controller. It allows you to use non-disk devices (such as CD ROMS) and higher capacity drives, as well as, take advantage of the PCI interface from your video card. It has a transfer rate of 11.1 MBps.³ It was adopted as a standard by the ANSI in 1994 as Advanced Technology Attachment-2 (Fast ATA), and offers faster access to the hard drive, support for Direct Memory Access and additional drives through the AT Attachment Packet Interface.⁵

So, what about the question? Does it really matter whether you use IDE or SCSI drives? Well, it depends on what kind of budget you have and what types of sites you are hosting.
To have a better idea of what should work for your needs, the following forum threads and articles are recommended reading:

• HostHideoutSCSI or IDE Hard Drives?
• Gurus Help! Quandry about hard drives to get...
• HostHideout -- SCSI or IDE drives?
• WebHostingTalk -- Dedicated Hosting Forum -- SCSI vs IDE
• WebHostingTalk -- Running a Web Hosting Business -- SCSI vs IDE
• DevChannel -- SCSI vs IDE: Which is really faster? by Gerard Beekmans
• Slashdot -- SCSI vs IDE in The Real World
• WebMastersWorld -- Dual Processors: How do they work?

But if you don’t have time to go through all those sites, here’s a summary for your consideration:

IDE drives

• have higher capacity and offer more value for your money, if you’re
• not hosting that many sites
  
• a good RAID card is a must
  
• do not support as high a data transfer as SCSI
  
• usually limited to a RAID 0+1 configuration
  
• more practical for http servers, unless your site requires high amounts of script executions or database queries

SCSI drives

• are more expensive
  
• offer lower access times and higher throughputs
  
• lower CPU usage when accessing
  
• capable of RAID 5 configuration
  
• not very beneficial if hosting a few sites and one drive per channel
  
• better for database-driven and high traffic sites since they process more I/O inquiries per second

You could also consider using IDE drives with SCSI adapters. IDE-to-SCSI adapters are expensive though, and according to Brave New World: Operating IDE Hard Drives on SCSI Host Adapters ‘make sense only if you can save a lot of money that would otherwise be spent on SCSI drives by running large IDE hard drives without having to resort to additional, expensive security measures (redundancy, spare drives, hot swapping cases).’

Article From: http://hostingvoice.com/hosting/000020.php

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