Date: Fri, 09 Jul 1999 01:39:25 -0700 From: The Clark Family <Clark@open.org> To: Greg Lehey <grog@lemis.com> Cc: mavery@mail.otherwhen.com, jsd@gamespot.com, freebsd-questions@FreeBSD.ORG Subject: Re: HP T4000s Tape Drive problems Message-ID: <199907090813.BAA15331@opengovt.open.org> In-Reply-To: <19990709112645.Q6035@freebie.lemis.com> References: <199907082224.PAA27606@opengovt.open.org> <199907082054.NAA03455@hudsucker.gamespot.com> <199907080218.VAA14937@hostigos.otherwhen.com> <199907082142.QAA16185@hostigos.otherwhen.com> <199907082224.PAA27606@opengovt.open.org>
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>>> Another consideration.... the 4000 series is rated at about 1.5mbps. >>> The 7000 at about 5... if memory serves. Many servers (your >>> hardware, backup software, server load, and OS will cause the >>> mileage to vary) can't deliver a byte stream fast enough to keep a >>> 7000 series drive in streaming mode, so it goes into start-stop mode. >>> This destroys the throughput.... slower than a 4000 series drive in >>> practice. So, unless you are VERY sure you have the bandwidth (and >>> more than one person has been surprised here), stay with a 4000 >>> series drive. Or two 4000 series drives for more capacity. >> >> The HP stuff is 4mil isn't it? If so, DAT is 8mil right? So HP isn't DAT >> its 4mil. > >DAT is 4mm digital audio. Video 8 is 8mm analogue video. > >HP is DDS, which uses the same form factor cartridges as DAT, but they >are *not* DAT. Most HP drives will reject DAT tapes unless you >override a configuration option. Different hole locations on the bottom of the tape? > >Exabyte uses the same form factor as Video 8, but again, the >cartridges are different. You're asking for trouble using Video 8 >cartridges in Exabytes: they'll work, sort of, but you'll get a much >higher soft error rate than with real data grade cartridges. And >there's really not much difference in price if you know where to shop; >I used to be able to get data cartridges cheaper than Video 8. They >worked fine in my video camera :-) > >> My theory is, if your servers can't keep up a stream of data >> sufficient to keep a DLT7000 streaming, then you need to rethink how >> you build servers. >> >> If you go with multiple 4000s, get three so you can stripe across them. >> (grin) > >I have a DLT4000. I can't keep it streaming, but it still goes faster >than my Exabyte and DDS drives. If you have any ideas on how to keep >it streaming, I'd be open to them. > Five channel Mylex RAID controller, i960 based Fast Ethernet NIC, Netware 3.X during off peak hours, feeding across a fast ethernet switch into a 486DX4-100 system running a two user copy of Netware 3.X dedicated to backing up system to a DLT4000 drive through a buslogic PCI SCSI controller. Cheyenne arcserver backup software, with compression happening on the server to keep network traffic down. Seems like the tape drive never stopped streaming. But before you point out some mistake of mine, that was two years ago, and the details aren't as clear now as they once were. >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 > Thanks again for the info. [RC] To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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