dww@stl.stc.co.uk (David Wright) (05/16/87)
I hear rumours of new tape drives offering >2000 MBytes of storage, using video
tapes or cartridges. Does anyone have hard information about such things,
and in particular does anyone have practical experience in using them?
We are currently putting together the budget/justification for an enhancement
to our computer system (uVAX's with VMS), and it would be nice if we could
solve the backup problem caused by lots of 600MByte disks. But only if the
new drives are reliable!
All help gratefully received.
--
Regards,
David Wright STL, London Road, Harlow, Essex CM17 9NA, U.K.
dww@stl.stc.co.uk <or> ...seismo!mcvax!ukc!stl!dww <or> PSI%234237100122::DWWjtk@mordor.s1.gov (Jordan Kare) (05/20/87)
In article <543@acer.stl.stc.co.uk> dww@stl.UUCP (David Wright) writes: >I hear rumours of new tape drives offering >2000 MBytes of storage, using video >tapes or cartridges. Does anyone have hard information about such things, >and in particular does anyone have practical experience in using them? > > David Wright STL, London Road, Harlow, Essex CM17 9NA, U.K. >dww@stl.stc.co.uk <or> ...seismo!mcvax!ukc!stl!dww <or> PSI%234237100122::DWW I cannot speak for commercial devices, but I built a videotape data recording system for storing digitized CCD images (for an automated astronomical telescope); it stores about 600 Mbytes on a 2-hour Beta tape, and we are rapidly approaching a terabyte stored. Videotape is a ghastly medium; with my (low density) storage scheme the bit error rate was about 10^-3, and errors tend to occur as long (up to >100 bit) dropouts. All videotape systems thus must use extensive error correction and/or redundancy; the "Vault" microcomputer backup of some years back used 6x redundancy. The combination of redundancy and inherently limited bandwidth (single channel recording) means the transfer rate is limited; possibly very limited (20K bytes/sec). Videotape is not particularly made as an archival medium (at least home tape) so unless you have excellent storage conditions (temp. controlled, dust free) don't expect tapes to last more than a year or so, or more than a few tens of "plays". "Consumer" tape decks are also not made for extended use; the heads must be cleaned frequently and replaced every ~500 hours. Also, of course, videotape is strictly a streaming medium, and VCR storage is not standardized (heck, even for _video_ there are 3 incompatible formats) so if your drive breaks you may not be able to find anyone else who can read your tapes. However, if you can live with these limits, videotape is hands down the cheapest storage medium available, both in cost per bit stored and cost per bit on line (drive cost/capacity). For non-archival backup use, if you can live with the low transfer rate, the only major concern is the lack of standardization. I would seriously consider getting at least two identical drives; otherwise, if your drive dies, you could find yourself in deep s... uh, trouble. Jordin Kare jtk@mordor.uucp