On Monday, 06/01/2009 at 03:32 EDT, "Hughes, Jim" <[email protected]> wrote: > I am looking at table 3 on page 10 of the 3590 Introduction and Planning > Guide. > > It mentions two things of interest: > Device Data Rate(native) and Data Transfer Rate(maximum instantaneous). > > Device Data Rate for the E11 is 14 MB/Sec. > Data Transfer Rate depends on the channel. > > I guess what I am reading says the tape will move around at 14 meg/sec > no matter how fast I get the data to the device. FICON for tapes is a > waste of time. > > When would FICON for tapes be a good idea?
1. When you have several on the same channel. Remember that the channel must carry traffic for multiple devices. At 14 MB/s, you can put 14 of them on a 200 MB/s channel before you saturate the channel. 2. When you're using 3592s. - TS1120s are rated at 100 MB/s (260 MB/s @ 3:1 compression) - TS1130s are rated at 160 MB/s (350 MB/s @ 3:1 compression) Even though latency (time before data touches the tape or is visible on the channel) is higher when encrypting or compressing data on newer drives, the heads transfer data to/from the tape at the same rate as raw data. As Tom says, if you stop the tape, then you incur the latency every time you restart the tape. Alan Altmark z/VM Development IBM Endicott
