lindsay@gandalf.cs.cmu.edu (Donald Lindsay) (04/08/91)
In article <1991Apr2.163914.7948@snitor.uucp> rmc@snitor.UUCP (Russell Crook) writes: >>There is a real need for a large backup medium right now. >Actually, there *is* such a beast (albeit rare and expensive) called >optical (write once) tape. A company called CREO (in Vancouver) >makes the drive (at something like 250,000$ or so), and a single >tape reel stores several terabytes (I believe). I rate optical tape as the bright hope for big, slow storage. ICI (the developers/manufacturers of the media) tell a very good story about density, permanence, and media cost. The questions now are the speed, price (and availability) of drives. CREO [604-437-6879] have apparently begun delivering a unit that puts 1 TB (yes, 1,000 GB) on an 880 m x 35 mm tape ( 12" reel ). I assume (well, hope) that the 3 MB/s SCSI interface was a marketing decision, not a technological limit. (It records at 0.1 IPS, but at ~ 1.5x1.5 micron^2 per bit, the writing lasers have to be scanned across the width of the tape.) LaserTape Systems [408-370-9064] have exciting vaporware: 50 GB in a cartridge mechanically compatible with the IBM 3480 (about like an 8-track audio tape). That buys them into 5,000-tape autochangers... -- Don D.C.Lindsay .. temporarily at Carnegie Mellon Robotics
davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr) (04/08/91)
In article <12608@pt.cs.cmu.edu> lindsay@gandalf.cs.cmu.edu (Donald Lindsay) writes: | I assume | (well, hope) that the 3 MB/s SCSI interface was a marketing decision, | not a technological limit. Well, a usefully high one. If you assume a fair sized file server might have a backup volume of 80GB per day, then 80GB/3MB is 26667 sec, or 7.4 hours. That's about right for an eight hour shift, and not having to pay an operator to hang tapes all night long would pay for the drive. Now the question is, how much is the media, and can you find a given place on it in a reasonable time? You could break the disk into small (200MB or so) filesystems in many cases, if you could write a filemark after each one and scan quickly through them. -- bill davidsen (davidsen@crdos1.crd.GE.COM -or- uunet!crdgw1!crdos1!davidsen) "Most of the VAX instructions are in microcode, but halt and no-op are in hardware for efficiency"
lindsay@gandalf.cs.cmu.edu (Donald Lindsay) (04/09/91)
In article <3318@crdos1.crd.ge.COM> davidsen@crdos1.crd.ge.com (bill davidsen) writes: > Now the question is, how much is the media, and can you find a given >place on it in a reasonable time? The media is polymer - mostly polyester - plus some organic dye and sputtered metal. If any volume at all develops, this should be competitive (in $/MB) with helical-scan mag tape, but shelf life should be a lot higher. Creo writes an address track with great big bits, that can be read during a fast scan. They claim their tape drive can random-access an 80 KB block in at most one minute. (Hey: a 24 bit address space!) Kodak and I are agreed on one thing: the rise of computerized images is going to push the whole storage question. -- Don D.C.Lindsay .. temporarily at Carnegie Mellon Robotics