Can you mix 10K and 15K SCSI drives...

[Hyun]

... in the same channel without performance degradation for either speed drives?

 

[Goosemaster]

absolutely, as long as they are both LVD

AS in a fast 15k 18GB Cheetah and a 10,000 73GB Seagate

Even a 7,200rpm 180GB drive


All that matters is that they are LVD

Obviously, Ultra2Wide LVd will make the channel slower, but regardless the drives are always independant of each other, and on some Adaptec cards this is now irrelevant

 

[Goosemaster]

By the way, I said 'as long as they are lvd'

because mixing LVD and non-LVD defaults to a slower interface....if I remember corectly...then again it might work at all.


Many adaptec cards such as the 19160 and the 29160 have two types of internal connections...LVD 68pin and non-LVD 50pin...obviously adpaters should be easy to find

 

[alkemyst]

depends on your controller as above in goose's post.

 

[dszd0g]

Yes you can mix 10K and 15K SCSI drives.

[Edit: Just make sure they both use the same kind of connector as your SCSI controller. In most cases, this just means avoiding SCA 80-pin hard drives.]

LVD is not the issue as Goosemaster posted. LVD (low voltage differential) is a physical layer communication protocol, as is HVD (high voltage differential), and non-differential (SE - Single Ended). However, to operate at Ultra2 Wide or above one must have all LVD devices on a bus, unless there is some sort of smart-negotiation on the controller. Some of the Adaptect controllers like the 29160 (With out the N, the N version does not have it from what I've heard). However, that smart negotiation adds overhead and has to share the bus and thus still slows things down.

The 68-pin connection is generally for Wide devices, while the 50-pin connection is for narrow devices. It just happens that there are no LVD narrow protocols currently.

Ideally, one should have all devices on the channel with the hard drive as Ultra160 (LVD). If one has SCSI CD and DVD drives (which are generally narrow devices that operate at Ultra), it is best to place them on a different channel. If a 39160 is not in your budget, than getting the 29160 (non-N) is the next best thing.

 

[dszd0g]

I would like to add that sometimes hard drives will be marked LVD/SE or one will hear of multi-mode SCSI, this is misleading and makes the user believe that the bus can operate at both LVD and SE at the same time. Unless the card supports special negotiation, the bus will drop down to SE if any SE devices are present. The fastest standard SE protocol is Ultra Wide (40MB/s).

However, this really isn't anything specific to LVD. On most controllers the slowest device determines the bus speed. Even if all devices are LVD if one is Ultra 2 Wide, one is Ultra 160, and one is Ultra 320 all three will operate at Ultra 2 Wide. Again the special negotiation that some adapters use gets around this.

Hopefully, this all isn't too confusing.

To answer the original question as simply as possible. Yes. To keep things as simple as possible for you try to match them to the same speed, Ultra 160 for example. If you can't, just assume that they will run at the slowest device's speed.