Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!spool.mu.edu!uunet!beartrk!ceilidh!dnichols From: dnichols@ceilidh.beartrack.com (DoN Nichols) Newsgroups: comp.periphs.scsi Subject: Re: High Capacity Tapes: Exabyte or DAT? Message-ID: <1991May29.012538.20996@ceilidh.beartrack.com> Date: 29 May 91 01:25:38 GMT Article-I.D.: ceilidh.1991May29.012538.20996 References: <29543@hydra.gatech.EDU> <9850023@hpcpbla.HP.COM> Organization: D and D Data, Vienna, VA. Lines: 31 In article <9850023@hpcpbla.HP.COM> mark@hpcpbla.HP.COM (Mark Simms) writes: [ ... ] >The DAT format has a lower capacity than the 8mm format although the use >of 90m tapes and on drive data compression will help remedy this in >future. DAT is shipped by at least three different vendors using This isn't one of my usual newsgroups, so this may have already been hashed out without my knowledge. My question concerns what happens when compression is in use, given that the drives become much less efficient when a block of a length not reasonably matched to the size of a single diagonal track (esp one just slightly larger) is written, and more data is not available at the time the drive writes the track. It would seem to me that the compression is likely to provide unpredictable length blocks of data being fed to the tape for fixed-length blocks coming from the system. How is the system to keep the blocksize optimum, especially if the data is coming from another system over ethernet? (Since delays in ethernet transfers may keep another block from being ready soon enough to use the rest of that track.) Thanks DoN. -- Donald Nichols (DoN.) | Voice (Days): (703) 664-1585 D&D Data | Voice (Eves): (703) 938-4564 Disclaimer: from here - None | Email: --- Black Holes are where God is dividing by zero ---