From: CSBVAX::MRGATE!RELAY-INFO-VAX@CRVAX.SRI.COM@SMTP 17-OCT-1988 09:17 To: ARISIA::EVERHART Subj: 8mm Tape Systems - Summary of Responses Received: From KL.SRI.COM by CRVAX.SRI.COM with TCP; Sat, 15 OCT 88 17:28:35 PDT Received: from bafb-ddnvax.arpa by KL.SRI.COM with TCP; Sat, 15 Oct 88 17:15:27 PDT Date: 15 Oct 88 19:14:00 CST From: "Jonathan L Wilson" Subject: 8mm Tape Systems - Summary of Responses To: "info-vax" Hello all- A few days ago I put out a query on the net for 8mm tape system war stories, and then again for news of an 8mm "jukebox" system. I got a lot of responses asking for a summary to be posted, so here goes: o All the 8mm drives store about 2 GB per cartridge. Some suppliers squeeze more space into a cartridge at the price of compatibility with other drives. A cartridge holds the equivalent of 14 2400' tapes or 50 at 1600 bpi. The capacity of the tape varies with the capability of the CPU to keep it streaming. o Some manufacturers require that you provide or patch the device driver (!) or controller. Read the specs carefully. TMSCP emulation (MUAx device names) is most desirable in a controller, since the drivers are supported by Digital. Some mentioned dissatisfaction with other types of interface (Dilog, etc.) that were not TMSCP. o Backup of 500 MB takes about 42 minutes on a Summus drive (8650 host). Corresponding time for a TU81+ magtape was 70 minutes. One correspondent measured 240KB/sec on a UNIBUS SCSI-interfaced 8mm drive (once the 40-sec startup overhead was over.) The general impression was that 8mm is about as fast as a TU78 at 6250 bpi when driven by a fast enough CPU. o The load/initialize sequence is measured in MINUTES. On large backups, though, this is inconsequential. o Q-Bus controllers are slightly faster than Unibus. o Summus is currently the only manufacturer with a "jukebox" arrangement. The Summus jukebox (going from a press release here) has 153 GB in a rack-mount enclosure for about $38K. Exabyte, which makes the drive itself for most suppliers, is coming out with a much improved jukebox soon. Honeywell, at least at one time, had a VHS jukebox; it may not have been interfaced to DEC equipment though. o The Summus drive, with Unibus controller, is about $7000 GSA. Other companies have slightly lower prices - a price war is driving prices down somewhat. o Media cost is calculated to be 0.4 cents per MB as opposed to 14 cents per MB for 9-track tape. 8mm tape are about $8 each, available at your friendly *-Mart. o Suggested backup parameters are /NOCRC along with a large block size, as you would expect. CRC is in hardware and using the /NOCRC reduces CPU time by about 70%. o Error handling seems to be good - media errors are infrequent. o The current issue of Digital Review announces a Systems Industries 8mm drive that will connect to an HSC. ----------------- Jon Wilson TRW D.S.G. / VAX Systems Manager / Brooks AFB Phone: (512) 536 2869 Email: WILSONJL@BAFB-DDNVAX.ARPA Disclaimer: The opinions expressed here are my own and not necessarily those of my employer.