Date: Fri, 9 Jul 1999 11:42:48 +0930 From: Greg Lehey <grog@lemis.com> To: The Clark Family <Clark@open.org> Cc: jsd@gamespot.com, freebsd-questions@FreeBSD.ORG Subject: Re: HP T4000s Tape Drive problems Message-ID: <19990709114248.R6035@freebie.lemis.com> In-Reply-To: <199907082224.PAA27583@opengovt.open.org>; from The Clark Family on Thu, Jul 08, 1999 at 03:46:14PM -0700 References: <199907080218.VAA14937@hostigos.otherwhen.com> <199907082054.NAA03455@hudsucker.gamespot.com> <199907082224.PAA27583@opengovt.open.org>
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On Thursday, 8 July 1999 at 15:46:14 -0700, The Clark Family wrote: > At 01:54 PM 7/8/99 -0700, you wrote: >>> I've resolved backup problems in several shops by just ditching the >>> Travan drives. These weren't the cheapos, they were the >>> "professional" NS-8 and NS-20 series drives. >> >> Based on what you and a few others have said about general Travan >> crappiness, I will follow your advice and put this thing back in >> the cupboard from whence it came, and instead play around with >> this Exabyte 8500 I found. >> >> On a somewhat related note, does anybody have any strong preferences >> between DAT/DLT/Exabyte? I'm interested in all experiences, good or >> bad... Let me know. > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-questions" in the body of the message >> From what I remember: > > Order that the equipment came out (from my vantage point): > > DDS-1 > DDS-2 > Exabyte (DAT) Exabyte is 8mm, not DAT. > DLT (4000) > DDS-3 > DLT (7000) > > This email is not intended to be a "standalone" communication, it probably > won't make much sense without a few emails passing back and forth. > > DDS-1 was the first tape format I was exposed to that wasn't based on QIC > (Quarter Inch Casette) technology. (Its based on a 4-mil derivative of DAT > and uses a helical-scan technology, like VCRs.) QIC has paseed into the > "attractive nusance" stage. > > I liked DDS-1, because it was fairly fast, fairly high capacity, and not > terribly expensive. I think we were getting the bare mechanisms from HP for > about 500$ (US) each. (2GB capacity, 4GB with compression, I think.) > > DDS-1 had one disadvantage, we couldn't run any of the drives for more than > three years (nightly backups) without them wearing out. You were doing well. I never got one to survive for a year. > DDS-2 was the tape format preferred by the UNIX heads at our shop. It was > very similar to DDS-1 (used the same tape), but featured hardware based > data compression. (4GB only) I'm not sure I understand this statement. You said above-- correctly--that you could get (about) 4GB out of a DDS-1 drive with compression (in fact, that would only be with 120m DDS-2 tapes; the longest DDS-1 tapes were 90m and would give you about 2.5 GB compressed). DDS-2 tapes were (are) only 120m, and they will give you 4GB uncompressed or about 8 GB compressed. > On UNIX, where the backup software was the definition of primitive, > hardware compression was the only type easily available. I don't understand this statement. > The hardware compression, and the fact that the UNIX guys bought > from higher priced VARs, made the DDS-2 stuff quite a bit more > expensive. Maybe 1k$ (US) per drive. It's not the compression that made them more expensive. They were a better technology, and lasted 18 months instead of 9. > I seem to remember that Exabyte jumped into the fray at this point. Exabyte have been around for over 10 years, since before DDS. > Their drives were based on 8-mil DAT technology, and because they > had more surface area, they had a higher capacity. In fact, there isn't much in it. The 8202 would only give you about 2 GB. > I had a SunOS running friend that had exclusively Exabyte. I tend to > see exabyte drives in Sun shops. I think Exabyte was trying to > appeal to the elitist part of the UNIX user. And to a degree, I > think they succeeded. That's where the market was when Exabyte started out. > There are at least three advantages to DLT. One, is the increase in > capacity. The native capacity of a DLT4000 tape is 20GB. Compressed is > 40GB. That is enough to handle most systems full-backup needs with one > tape. (RAID arrays.) > > Second, is their speed. I don't remember the numbers off the top of my > head, but 20MB / second seems to ring a bell. Nowhere near. From http://online1.quantum.com/products/dlt/dlt4000/dlt_4000_features.htm: Features and Benefits High performance 1.5 MB per second native transfer rate High capacity 20 GB native capacity High reliability and durability Backward compatibility to previous DLTtape formats > Third, is the fact that they use a relatively low-tech approach to tape > utilization. In other words, they don't (seem to) suffer the wear out > problems that I've seen with helical scan tape drives. Comparing the MTBF > numbers, and my personal experience with helical scan tape drives, I > wouldn't be supprised to see DLT drives work for 10years. (Hopefully > they'll be obsoleted though.) > > DLT does also have some pitfalls: > > One, is that they are expensive. I seem to remember that it was usual for > the DLT4000 to go for about 4k$ when the first came out. The disk drive depot in Sunnyvale is currently selling refurb units for $995. But the tapes are *really* *expensive*. > Second, is that it takes quite a while for the tapes to load load and > unload. This can be a problem in tape jukeboxes, or if you tend to need > bits of data off the tapes often. They're still faster than Exabyte, and on par with DDS. Greg -- When replying to this message, please copy the original recipients. For more information, see http://www.lemis.com/questions.html See complete headers for address, home page and phone numbers finger grog@lemis.com for PGP public key To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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