Fibre Channel's advantage over SCSI

[Michael Chen_2]

I have a 1200MX optical jukebox connect with my NT server using conventional SCSI cable. My NT server is only 3 feet away from the jukebox, and the speed of read/write image from the server to the jukebox is critical. I was suggested to use Fibre Channel to SCSI bridge to take advantage of the speed of Fibre. What I don't understand is how much fast (50%, 100% or more) this Fibre Channel to SCSI bridge can give me over onventional SCSI. And how can Fibre Channnel exceed the max data transfer speed of SCSI? I can't find any hard data to support Fibre Channel's advantage over SCSI. Thanks for your help.

[Quin Hammes]

Micheal,
What kind of SCSI do you have? Ultra2, Wide Ultra2, Ultra160?

Ultra2 does around 40 MN/sec
Wide Ultra2 does around 80 MB/sec
Ultra160 does around 160 MB/sec

Fibre is gigabit which means that it does 100 MB/sec.

Using fibre though is not going to help you. You will still have a SCSI bottleneck in the path. The data is going to be leaving the jukebox at 80 MB/sec (lets assume Wide Ultra2). It then hits the bridge where it is converted to fibre and goes at 100 MB/sec. This does not get you anything because the data is still going to be coming out of the jukebox at 80. The conversion down the path will not increase that speed.

Fibre is costly (2-3 K per card on NT) and a bridge is costly also. I would suggest taking the money you would have spent on the fibre equipment and invest in more RAM, another system to handle the load possibly, faster internal disks, cpu upgrade etc... This will probably help performance more than anything you can get by adding fibre.

Just my two cents but I think I am right.

Quin

[Bill McNAMARA_1]

FC because it's optically based is less prone to interference.

Also, bus errors and hardware repair is much more straight forward with FC. It doesn't require systems to be powered off to remove cables.

The FC to SCSI bridge will give you the same rate. The bottleneck is on the scsi bus, not on the FC loop. If it's going to be critical upgrade your jukebox.

Later,
Bill

[harry d brown jr]

If you had FC all the way to the jukebox and into the drives within, then FC makes sense, but if you are pushing data at a rate that is flooding the scsi on the jukebox then FC is not going to help.

[Leif Halvarsson_2]

Hi

There is a common misunderstanding about Fibre Channel, the main advantage (and idea) with FC is not speed but connectivity. This can be long distance, ablity to share devices between multiple host, large number of devices etc.. If you only want to connect one external device (for example a jukebox), located close to your server there is no need (and hardly any advantage) with FC, you can reach the same speed with SCSI (depending on which SCSI bus you use).