Please explain Master/Slave on Eide and how to pick..

[you2]

Does anyone have a pointer to a faq or can answer this question outright --

What exactly are the implications of master/slave channels on eide bus.

For example -- I am setting up a new system with three eide devices (7200 rpm hard drive, dvd/cd player, and cdrw drive). What should go where and why?

I would have thought it would be cdrw master, dvd master, harddrive slave to dvd.

However, I was told hd master, dvd master, cdrw slave to dvd.

Vaguely, I thought that the master had priority over the slave - so wouldn't it be better to put the cdrw as msater somewhere ?

Also is it better to put slower device or faster device on master or salve ?

I guess I'm looking for both and also an explanation as to why a given answer...

thanks,

 

[AndyHui]

Hard drive should always be primary master.

Usually we recommend the CDRW as secondary master and DVD as secondary slave, as this usually allows you to do direct copies on the fly from the DVD drive to the CDRW.

 

[you2]

More confusion -- does this mean the primary and secondary channels are not equal ? How dose priority work with slave of primary to master of secondary?

 

[AndyHui]

They are equal in terms of performance, although the main difference lies in software.

Operating systems usually talk to the Primary master first (it's a lot more complex than that, but this is a very simplified explanation).

 

[kgraeme]

Here's a good guide..

Basics:
- Each cable supports a master drive and a slave drive.
- The OS should generally be installed on a master drive on the first ide bus (usually bus 0) because this is where the bios expects it to be.
- There are generally two ports for cables on the motherboard. Each is a separate "channel".
- Master and slave drives can be equally fast, priority really isn't an issue these days.
- When one drive on the cable is working the other drive on that cable is idle. Because of this, transfers between drives on the same channel (cable) are slower than transfers between two drives on seperate channels.
- Besides the boot drive, some drives prefer to be master. Both my DVD and CDRW would prefer to be masters. They work fine as slaves though.

Sorry if that is overly pedantic, but you asked for a FAQ.

Basically you need to consider what drives are most commonly going to be copying to/from each other and put them on seperate cables. For most people with a cdrw, they want to either write from the HD to the CDRW or from the CD/DVD to the CDRW. That means that the CDRW needs to be on a different channel than either of these two. A DVD during movie playback only needs to play at 1x dvd speed, so sharing it on the same channel as the HD isn't going to have any significant impact.

Configuration:
IDE0: Boot HD (master), DVD (slave).
IDE1: CDRW

If you were to add another hard drive to your system for storage, you would probably want to add it to the second IDE channel. Whether you use master or slave isn't going to be a significant issue, but by convention the HD would be master.

 

[acejj26]

i agree with kgraeme

the cd burner will be getting its data from one of two sources....the dvd drive or the hard drive.....therefore, neither of those devices should be on the same channel as the burner. and since the hard drive should be the master, it only follows that kgraeme's recommendation should be followed

 

[dunkster]

The optimum solution is to assign each device to a dedicated IDE port, eliminating any master/slave configurations and allowing maximum efficiency when writing to any IDE device from any other IDE device. In your system, you have three IDE devices with only two IDE ports.

NewEgg offers Promise IDE adapter cards for $23. These cards are PCI plug-ins that provide two additional IDE ports, which would allow each of your IDE devices to be a master on it's own IDE port - with one IDE port left over for an additional IDE expansion device.

The only reason I bought a RAID board was to get the two additional IDE ports.

Hope this helps!

 

[you2]

Thanks Kgraeme. The details you were provided presented a good general overview. You were also the only one to suggest the dvd and hard-drive be on the same controller.
Should work fine. I'm sticking some older (1gb) scsi drives in the system and I'll setup freebsd swap space to those. Hum... another ide controller. If Kgraeme description is accurate I
would think his configuration would be fine for these three drives. At worse - if I run something disk intensive in the background the dvd drive will stutter while playing music or a movie.
Right? Doesn't sound too harmful.

 

[kgraeme]

Glad I made sense for once. I can assure you that the setup I suggested works nicely since it is exactly what I have at home.