The difference between SCSI & IDE Hard disks.

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# 1  
Old 12-02-2002
The difference between SCSI & IDE Hard disks.

Hello agian !

What is the difference between SCSI and IDE hard disks ?
I have Intel PC and when i check i have Generic IDE TYPE DISK0

is IDE hard disk is ok for Solrais ? or should i buy the SCSI hard disk ?


Abid Malik
# 2  
Old 12-02-2002
SCSI and IDE are two different types of interface. They use different disks, controlers, cables, etc to attach to your PC. SCSI is generally faster, more expandable, and more reliable than IDE. It is also much more expensive. IDE disks can be used with the Intel version of Solaris, as long as they are recognized by the BIOS.
# 3  
Old 12-02-2002
An important difference between SCSI and IDE is that SCSI can handle multiple devices on one device chain. Currently it supports 15 separate addresses (hundreds more if you count LUN's). IDE, however, only supports 2 devices on one chain, a master and a slave.

Another critical difference is that the SCSI bus can send and receive data from all of the devices on its chain at the same time whereas the IDE bus can only access one device at a time.
# 4  
Old 12-05-2002
Our firm started and maintained the Linux Benchmarks for many years (and then retired them). During that time we received many benchmarks for all kinds of UNIX and Linux systems (including HP-UX, Sun, and more), thousands of Byte UNIX Benchmarks (see for the 'retirement page').

Before running the Benchmarks, I was a firm believer that SCSI outperforms IDE. After reviewing and ranking over a thousand benchmarks, it became obvious that, in general, SCSI-based UNIX or LINUX systems DO NOT outperform EIDE based systems. Yes, the raw numbers show that SCSI is faster, but this does not appear in any noticeable (useful) benchmark output.

In fact, given the same OS, MB, CPU, Memory, etc. sometimes EIDE systems seems to outperform SCSI.

SCSI tends to 'crap out' also.... one bad or misconfigured termination and your machine is dead. EIDE does not have this problem.

So, unless you are the very rare person who needs to attach 7 devices to a host adapter versus 2, or need the (perhaps not realizable) speed of a SCSI(n) interface; any gain in speed (perhaps none) is greatly lost in the negatives: less reliability and a much greater cost.

On the other hand, if you are running a configuration (like HP-UX ServiceGuard) or similar system that can failover CPUs and attach a single disk, you must use a SCSI bus. It cannot be done (to my knowledge) with an EIDE bus.

For 99.9 percent of the users in the world, EIDE offers comparable performance and at a much less cost with much less complexity.

The bottom line:

After running the Linux Benchmarks for a few years, I retired all SCSI host adapters and disks on all our home office systems. So, for the average home UNIX or Linux user, go EIDE. Big businesses with other requirements are another story; the original poster (with an Intel PC) is more-than-likely a user who does not need SCSI.
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