Placing the hard drives on separate channels

[Larkina]

Will placing the hard drives on separate IDE channels yield good performance? The way I understand this is that the Primary hard drive is placed with the CD-Rom on the same channel with the pin connection in the Slave position. Next the second hard drive would be placed on the second IDE channel with the CD or DVD as the Primary and the hard drive as the Slave. If this is right, will this support a striped configuration? More important is the pin connection. I guess the pin connection would mirror each other in other words, hard drive (primary),CD, (Slave) and then CD, (primary), hard drive, (Slave). I could be all together wrong with this. Could someone give a senior citizen some help please. It really would be appreciated. Thank you in advance.

[Jim]

Here's my understanding of the situation, but I'm sure someone with actual tech know-how will step in and fill in the gaps soon enough.

Most optical disc drives are ATA-33, while I would assume most HDDs are either ATA-100 or 133 these days. When connecting drives of different speeds on the same cable, the drives will default to the speed of the slowest device connected. In other words, the HDD will be running at ATA-33 speeds if it's being connected to the same cable as the CD/DVD drive.

Performance-wise, you'll do better with both HDDs and both optical disc drives being connected on their own channels.

[Larkina]

Thank you for the help Jim. I'm always looking for a little more speed and better performance. I guess I'll have to actually just purchase one of the high performance models. Thank you.

[YARDofSTUF]

Wiki = God of almost useless info

Mixed Device Speeds

It is a common misconception that, if two devices of different speed capabilities are on the same cable, both will necessarily transfer data at the speed of the slower device. This is true only with very old chipsets or add-in adapters. All modern ATA interfaces (since, at least, the late Pentium III and AMD K7 era) support independent timing, which allows each device on the cable to transfer data at its own best speed.

However, due to the omission of both overlapped and queued feature sets from most real-world parallel ATA products, the preceding paragraph must be clarified. It applies to the data transfer phase, but this is usually the shortest part of a complete read or write operation. Devices do differ markedly in the total time required to perform an I/O (irrespective of the burst data transfer rate), and since only one device on a cable can have an operation in progress at one time, they do affect each others' performance.

For example, consider an optical device such as a DVD-ROM, and a hard drive on the same parallel ATA cable. With average seek and rotation speeds for such devices, a read operation to the DVD-ROM will take an average of around 100 milliseconds, while a typical fast parallel ATA hard drive can complete a read or write in less than 10 milliseconds.

This means that the hard drive, if unencumbered, could perform more than 100 operations per second (and far more than that if only short head movements are involved). But since the devices are on the same cable, once a "read" command is given to the DVD-ROM, the hard drive will be inaccessible (and idle) for as long as it takes the DVD-ROM to complete its read—seek time included. Frequent accesses to the DVD-ROM will therefore vastly reduce the maximum throughput available from the hard drive. If the DVD-ROM is kept busy with average-duration requests, and if the host operating system driver sends commands to the two drives in a strict "round robin" fashion, then the hard drive will be limited to about 10 operations per second while the DVD-ROM is in use... even though the burst data transfers to and from the hard drive still happen at the hard drive's usual speed.

The impact of this on a system's performance depends on application. For example, when copying data from an optical drive to a hard drive (such as during software installation), this effect probably doesn't matter: Such jobs are necessarily limited by the speed of the optical drive no matter where it is. But if the hard drive in question is also expected to provide good throughput for other tasks at the same time, it probably should not be on the same cable as the optical drive.

On the other hand, it is worth emphasizing that this effect only occurs if the slow drive is actually being accessed. If it is idle, its mere presence on the cable will not affect the performance of any other device on the same cable (provided, of course, that the host adapter supports independent timing).

More than you will ever want to know about ATA cables and standards:
http://en.wikipedia.org/wiki/Advanced_T ... Attachment

Basically, what you want to do is have the OS drive and the least used optical drive on IDE 0(The first one) and the other hard drive and optical drive on IDE1, some times there IDE 1 and IDE 2.

This way when the optical media needs to be read it wont interfere with the OS wanting to read off its drive.

Now if your PC is basically just for burning you may want the OS drive and the most common burner on the same cable, so that you can have a nice flow of data by storing the burned files on the second hard drive, thats on the second cable and then send them to the burner on the first cable.

[Larkina]

So in essence what you are saying is that this can work and yield great perfomance provided that everything is setup properly, pins, placing the hard drives on the right IDE along with the optical equipment. Yesssss!

[YeOldeStonecat]

I prefer separate controllers.

[Larkina]

Thank you'll for the great information. You guys are tough.

[Larkina]

In order to place both hard drives on separate channels would I need any extra cables? Currently I have 2 hard drives, a CD-ROM and a CD/DVD optical. Would I need any extra cable in order to perform a separate channel configuration? My computer is a fairly new model, (Dell Dimension 4500). It has the regular 3-way connection, motherboard, master and slave connection ribbon, ( 40 pin plugs.) I'm using 2 Western Digital 7200 rpm. hard drives, 1 80G and 1 40G. My 40G being the latest but whenever performing a clean install my 80 always comes up first which I took that to mean the 80G is the fastest of the 2 hard drive units.

[YARDofSTUF]

To put everything on its own cable you would need to buy an ata controller card, but to splt the hard drices you just put each hard drive on a master on each cable and then both cd roms go to the slaves.

[Larkina]

Thanks a million.

[Larkina]

I'm just a little confused as to how you physically change your IDE cables to accomodate a hard drive and a cd-rom. My IDE cable won't reach that far due to the way the hard drive bay and cd bay's are located in my computer case or is this automatically done when you set both hard drives to master and the opticals to slave?

[YARDofSTUF]

Well you need it to reach so that 1 hard drive and 1 cd rom are on each cable, otehrwise you cant make it work. that happens sometimes with cases, it may not be an option for you.

[Larkina]

That's exactly what I was thinking also. Thank you very much for the help anyhow.

[YARDofSTUF]

No trouble