Date: Mon, 23 Dec 1996 22:56:02 +0000 From: Simon Reading <aat81@dial.pipex.com> To: grog@lemis.de, se@freebsd.org, freebsd-hardware@freebsd.org Subject: DAT reliability Message-ID: <3.0.32.19961223225320.006855dc@pop.dial.pipex.com>
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Thanks to those of you who are participating in this thread. In my original post: >I had an HP C1533A DDS-2 drive which worked fine, but which I exchanged for a sony SDT-7000 DDS-2 because of the reliability warnings given in the FreeBSD Handbook. Unfortunately my sony drive is broken - I/O errors on read, can't format tapes using the Adaptec EZ-SCSI utility etc. In this email, I explain what my setup was for both the HP and Sony DDS drives. I RETURNED THE SONY TODAY because it was the last day I could do so and get my money back. I have not purchased a replacement yet as my choice is dependent on the outcome of this thread :-) I think there are a number of issues: + How reliable is DDS/DDS-2 (DAT) technology? + Is any one brand of DDS drive better or worse than another? (or 'Do the HP drives warrant their Freebsd warnings?') + Can anything be done to extend DDS drive life? + Is there a common failure mode for DDS? >From mail that I have received I am beginning to believe that the DDS mechanism, or more precisely the head, wears out and break down. I don't know if HP drives are better or worse than any others. That said, I have been put off the Sony SDT-7000 as 1) my problems with the unit supplied to me, 2) on the basis of replies, few seem to be in circulation (are sony users at bleeding edge?) and 3) I can't see how the high rotational speed of the SDT 7000 can do anything but degrade reliability (cf HP). Dave (dtsao@puc.edu) wrote: >If you can purchase the Sony 7000 for $40 more than the Sony 5000 DAT, and >the *only* difference is that the 7000's RPM is 8503 while the 5000's is >4000, would you buy the 7000? Is it as reliable and safe when running at >that speed? My HDD doesn't even come close! On the general subject of DAT reliability, phr@netcom.com (Paul Rubin) writes: >I have a C1533a now a little over 1 year old. I've had no problems >with it but my usage has been pretty light. Any DAT drive will >wear out after a year or so of heavy usage. DAT is built around >consumer audio media designed for low cost, and the mechanisms >are too fiddly to be really durable. Same goes for 8mm only more so. >If you want reliable backup and can pay for it, get DLT. Otherwise >DAT is the best bet. Unfortunately I can't afford DLT, so DAT it is . . Greg Lehey <grog@lemis.de> enquired of my setup: >> He really wasn't that clear about what didn't work for him, >> and it may be something silly like using audio grade tapes, >> which can't be written to (unless some DIP switch is set to >> a non-default position, which might have been the case for >> his HP drive). > >Yes, that's correct. It was one of the problems I was thinking of, >too. Let's wait for his reply. Here are my setup details: Hardware setup 1: Adaptec 2940 (non ultra) HP C1533A DDS-2 (internal, connected via adaptec internal cable). The DAT drive is the only device on the SCSI chain. Tapes which I used successfully on the C1533A: + HP DDS 60 metre. + Sony 90 metre computer grade DDS-2. Dip switch settings: + Compression enabled at power on, with host control. + Media recognition active. + Caution on hard error. + Parity on. + Data phase disc. + Truncate request sense off. + Variable block size mode. + SCSI id 3 Hardware setup 2: Unsuccesful Setup with sony SDT-7000 (connection as above). + SCSI id same as for HP DAT + DC disable (tried both ON and OFF) - what is this? + SCSI parity on. (both settings tried) + Termination on. (both settings tried) The Sony package which I received had evidence that it had been opened (a faulty return?). Problems with the sony were: - Excessive lacing and unlacing of the tape on boot up (it really seemed to be making a meal of it). - Inability to format Sony DDS-2 tape using the Adaptec EZ-SCSI utility: (read errors, tape removed from drive during format etc). - device I/O errors when trying to read a tar archive created by the HP and another DDS drive. Simon
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