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What is a Disk Controller?

Posted on 2009-07-04
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Hello,

It's a pretty simple question I know.

When I hear the term "disk controller" I don't understand what's being referred to exactly.

So for example, I'm studying Oracle and they suggest putting the files on separate "Disks" as well as separate "Disk Controllers.'

I know what a hard disk is.

So in my PC for example, I have a 300 GB hard disk.
What would be its "disk controller?"

In a RAID setup for example, I can picture a set of different "hard disks", what would be its "disk controller?"

Is SCSI a disk controller?

Any feedback would be much appreciated.
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Question by:ora-what
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Lee W, MVP earned 500 total points
ID: 24778761
The disk controller is the device that is allowing the hard disk to interface with the rest of the system.  

Virtually all "consumer" systems, such as your home computer, has the controller build in to the motherboard - it's the electronics "behind" (metaphorically and not necessarily physically speaking) the SATA (or IDE) plug on the motherboard.

Oracle expects to be on a server.  Servers CAN have integrated controllers, but they often use separate I/O cards like this:
http://www.newegg.com/Product/Product.aspx?Item=N82E16816117043

So having separate controllers, you would need, obviously, two of these (controllers like these), where one drive is connected to each (or one set of RAID drives is connected to each).
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by:theklap
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by:Frosty555
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"Partitions" or "Logical Disks" refers to partitions on a single hard drive in the computer
"Physical Disks" or just "Disks" refers to the physical hard drives in the computer
"Disk Controller" refers to the interface or bus lines used to communicate with that physical hard drive.

So, as an example, with IDE drives your computer typicall has two IDE ports on it. Each IDE ribbon cable has two plugs on it. You can connect two hard drives to each IDE port, for a total of 4 hard drives in your system. In this case, you have two disk controllers (the primary and secondary IDE ports). And each disk controller can have two disks on it (the master and slave).

How bus lines are shared for sata devices... i'm not 100% sure. I expect that on the less expensive motherboards all the sata ports will share a single controller, but on more expensive motherboards you may have two or more controllers. Perhaps this is why on some motherboards you have 2 black sata ports and 2 red sata ports? I'm not sure, hopefully somebody else can clarify.
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by:Frosty555
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I'm thinking that the whole idea behind Oracle suggesting you should put the files on separate disk controllers is that it provides one more layer of redundancy for failure situations. If your disk controller controlled several disks, and the controller went down, all disks on that controller would then cease to function. It's something to keep in mind when you are deciding where you files are going to go.

Also if several disks are communicating on one bus, they obviously have to share the bandwidth of that bus. There is more performance to be had if they were on separate buses.
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Disk Controllers are the part of the motherboard chipset that handles how many data channels you have, drives you can connect to each channel, and how the computer talks to the disk.

If you get an addon card, it has it's own chip that tell those same things.

IDE {PATA-SATA)
SCSI
SAS
RAID
are just different ways for the computer to talk to the drives. Sort of like a language.
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Wow!   Where did all those come from?  8 0
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