Date: Tue, 30 Jun 1998 15:17:18 -1000 From: richard@pegasus.com (Richard Foulk) To: freebsd-hardware@FreeBSD.ORG Subject: Re: Strong opinions, anyone? Message-ID: <199807010117.PAA20095@pegasus.com> In-Reply-To: Greg Lehey <grog@lemis.com> "Re: Strong opinions, anyone?" (Jul 1, 9:01am)
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} > There have been little glitches along the way. When they first came } > out, a very long time ago, they had a few problems here and there. } > } > They're quite solid now. } } Right. The newer Exabytes are a whole lot better than the old ones. The last six or eight years worth of 8200's have been solid too. } In particular, it appears that the drum life has been extended by an } order of magnitude. The 8200 is not a newer Exabyte, and if you buy a } refurbished one, you're running the risk of drum failure in the short } term. [...] The newer ones are better. The 8200's are way cheap and fairly robust, especially when compared to their competition in that price/capacity segment. } [...] Note also that the drive firmware hides a lot of the retries. Bull. The drive hides the retries by default. It is possible to query the drive for the soft error count. That's were you see the incredible redundancy of this design. About a decade ago when they got most of the bugs out of the 8200 we tried a number of different brands of tape. The way-cheap junk brands would sometimes have hundreds of soft errors in 2 Gigs. The Sony tapes would show no soft errors at all! Zero. Crummy, worn-out tapes that work poorly even for video will still work for data on the Exabyte. (Not that you'd really want to use them.) } > I like being able to buy tapes at the corner drug store if I need to. } > Unlike the newer, higher capacity Exabytes the 8200's were designed to } > use consumer video tapes. (The newer ones require `data quality' tapes.) } } You can set the new ones to use consumer tapes, too, I think. [...] No you can't. Exabyte is fairly emphatic about that. The data quality tapes are much smoother and cause much less head wear. } [...] Since } the tapes are no cheaper, and the dropout rate is much higher, I can't } see any reason to do this. I strongly recommend buying data grade tapes. The video tapes are *way* cheaper. The good Sony tapes are available from various discount stores for around $3. } > I've got some eight and 10-year old tapes written on various drives } > that are still readable today. Even readable on the new high-capacity } > drives. Amazing. } } That doesn't surprise me. } } > No doubt there will soon be some higher capacity drives that are } > as reliable and as inexpensive to use (media is part of the cost.) } > Just not yet. } } What about DDS-2? You can get up to 7 GB on a 120m tape, and the } units cost in the order of $700 new. DDS-3 will store still more, but } they're also more expensive. Out of my price range. Even before you look at media prices. } } In general, I'd say that the serious (as opposed to high-end) tape } market is dominated by helical scan units based on consumer cartridge } formats. Exabyte is based on 8mm video tape, and DDS is based on DAT } (digital audio tape). In each case, the medium cost is low and the } data capacity is between 2 and 14 GB. Both systems offer data } compression, which in my experience (including backing up a lot of } gzipped files) gives a storage improvement of about 90%. DDS drives } tend to be cheaper, possibly because of the number of manufacturers } out there. The reliability of *all* helical scan drives used to be } barely acceptable, and has since got much better: as a result, I don't } recommend buying older helical scan devices. } All 8mm drives are format and compression compatible assuming the same or greater capacity on the readers side. This is not the case with DDS. A number of incompatibilities exist. I know I can trade data with someone else with an 8mm drive. Chances are two 4mm drives cannot. And average reliability on DDS is about even with the aging 8200. DDS doesn't have the real estate to provide the redundancy that 8mm does. Richard To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message
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