scsi transfer rates

[jungle]

ok if you got a pair of LVD ultra wide 2 80mb drives, and you add an LVD ultrawide tape backup; will it slow the hard drives down?

I need to put a tape b/u in this server but i really don't want to add a 2nd LVD controller in it, but I also would rather not slow down the existing hard drives that are in use.

tia...

 

[Nothinman]

Newer controllers have a feature that lets it run different speed 68-pin drives at their own speeds even on the same wire, don't think it includes 50-pin ones with a converter though, see if your controller does that. I doubt it does since it's probably pretty old, if the controller has a second port you could use that and it shouldn't slow down the drives.

 

[Peter]

The capability of running any drive at its unique best speed has ever been present in SCSI.

There is a borderline: If you add a non-LVD device to an LVD capable channel, you'll lose the LVD-ness altogether. So mixing anything from original SCSI to Ultra-Wide is perfectly OK, and so is mixing U2 and U160.

regards, Peter

 

[SCSIRAID]

You didnt mention what SCSI controller you had in the system. Is it LVD also? As Peter said you can mix device types and SCSI will adjust properly and work (just perhaps not in LVD mode). It is best if everything is LVD due to the better signal quality of an LVD diff pair signalling scheme. Adding an additional device (such as the tape drive) to a SCSI bus always has the possibility of impacting performance. If the tape drive is quite fast (like a SuperDLT) then it will utilize a possibly signifigant portion of the busses bandwidth. In general though.. with two older drives.. you are probably fine. Most SERVERS run a small block random drive workload which doesnt stress the bus bandwidth. YMMV

 

[jungle]

the controller on this pc is an anadaptec 2940uw2 (on the the mobo). it has one uw2/lvd connector, a uw connector, and a 50 connector.

currently there is 2 lvd 80mb/s drives on the uw2 controller.

 

[SCSIRAID]

I dont believe an Adaptec 2940UW is LVD... Its Ultra. The 2940U2W is Ultra 2 LVD.

 

[jungle]

opps..my bad this is a UW2

 

[RSMemphis]

It should work without a problem. SCSI has no difficulties negotiating individual speeds.
If your controller were SE, it would not matter anyway.
But it seems your controller is LVD, so are the HDs and you said the tape drive, too.

Well, plug it in, go into the bios of the SCSI controller, there you can check the speeds negotiated.