Single channel IDE RAID

[PKRipper1]

I've used RAID setups for years now. I've used 2 IDE channels and 2 SATA channels but I don't understand how you can RAID with a single IDE channel. Can someone please explain?

 

[crispy2010]

I could never understand this myself. I would guess the single channel has the bandwith to handle both.

 

[Lord Evermore]

The problem is not bandwidth, it's that on a single IDE channel, only one device can be communicating at a time. For RAID0, this means that the chipset has to send data to one drive, wait for whatever acknowledgements, then send the stripe of data to the other drive, wait for the ack, back and forth. It's still faster than just a single drive, presumably, because the controller doesn't actually have to wait for the mechanical write of the data, but it's not the simultaneous read/write of independent channels.

There's no technical reason for it not to work, it's just not an optimal setup. With RAID1 it would actually probably be slower performing, since you're in essence having to wait the same amount of time for each drive to be written to as you would for a single drive, so you get twice the latency. Reads would still be only as fast as a single drive probably.

 

[corkyg]

My mobo makes such a thing possible. There is a separate IDE RAID connector, and if you plug in but one drive, it has to be RAID 0. It also allows for a PATA drive to be in a RAID array with a SATA drive. That is really why it is there.

SO, it is possible, but really of not much consequence.

 

[Lord Evermore]

I thought he was asking about using RAID with 2 drives on a single IDE channel, not bridging RAID between IDE and SATA channels.

 

[PKRipper1]

Lord Evermore, you are exactly right. That is my question.

Thanks, Paul

 

[corkyg]

That being the case, there is no tangible benefit to using a single drive in a RAID array. It has to RAID 0, but it really only amounts to being able to use a different controller. My mobo (Asus P4PE) has an optional ATA 133 IDE (PATA) RAID port. The RAID controller handles both PATA and SATA arrays.

But - it can be done. I can have a single drive on that port. benefit? None that I am aware of except to have another blue IDE port available.

This is a good read on the overall subject:

RAID

 

[Lord Evermore]

And to point it out again, he was talking about 2 drives on a single channel, not a single drive.

 

[corkyg]

Originally posted by: Lord Evermore
And to point it out again, he was talking about 2 drives on a single channel, not a single drive.

Exactly. I thought that it was adequately explained in the article. My mobo allows it. Two drives on one cable using CSEL. It is not the normal IDE port, but a special IDE port that incorporates the mobo's RAID controller.