ockenden@prlhp1.prl.philips.co.uk (Paul T Ockenden) (10/13/88)
We've just a very interesting conversation with DEC (here in the UK) after one of our TK50 drives went wrong (for about the 6th time in 2 years). We noticed that we were getting a fairly high error count, even on the new drive the engineer just installed, so we 'phoned round various DEC departments to find out what the acceptable error rate for TK50s was... DEC say that it's normally 50-72 (don't ask me how they got 72!!) for a TK50, and 'anything over 100' for TK70s... Now whilst I realise that these are soft errors, and nearly always they turn out to be recoverable, the added processing (plus tape positioning) involved in servicing 70 errors must increase the backup time considerably. (or am I wrong ???) What have DEC told other users for an acceptable error rate for TK drives ?? Incidentally....... While the DEC engineer was in fixing the TK50, he let slip that he pays more visits to clients fixing the 'supposedly' more reliable TK70 drives than he does TK50s.... As TK70s are fairly new to the UK, and as we've got one on order, can anyone comment for me on just how reliable they are ??? Thanks... . -- Paul Ockenden uucp : ....uunet!prlb2!prlhp1!ockenden Software type person ....mcvax!ukc!prlhp1!ockenden Somewhere in England. janet : ockenden%prlhp1@uk.ac.ukc "Blah blah blah......... (Pizza Killers!)" bix : paulock cix : PaulO
davew@gvgpsa.GVG.TEK.COM (David C. White) (10/19/88)
In article <654@prlhp1.prl.philips.co.uk> ockenden@prlhp1.prl.philips.co.uk (Paul T Ockenden) writes: >We've just a very interesting conversation with DEC (here in the UK) >after one of our TK50 drives went wrong (for about the 6th time in >2 years). > We've had ours for over 2 years now without a failure. There was an infantile failure in the original when the little strap that grabs the leader got shredded. They replaced the whole drive because at the time the part was not available except as part of the drive. >Now whilst I realise that these are soft errors, and nearly always they >turn out to be recoverable, the added processing (plus tape positioning) >involved in servicing 70 errors must increase the backup time considerably. >(or am I wrong ???) I haven't noticed any degradation in the backup time. The tape seems to be in streaming mode every time I listen to it. The thing that made the real difference was when DEC rewrote the Ultrix TK50 driver a few versions back. The first couple versions of Ultrix couldn't even get the TK50 going in streaming mode for backups. >What have DEC told other users for an acceptable error rate for TK drives ?? I haven't been given any specific numbers other than our service engineer telling me that the error rates I was seeing in the logs were normal, whatever that means. >As TK70s are fairly new to >the UK, and as we've got one on order, can anyone comment for me on just >how reliable they are ??? We've had our 3600 with a TK70 for about 6 months now and the drive hasn't failed yet. I have had two strange lockups in the controller that required a reboot of the system to cure. Other than that, no problems. In contradiction to the higher error counts that DEC said were common with the TK70, I can only say that I very seldom see any tape errors in the error logs on the 3600 with the TK70, but our MVAX II, with the TK50, error logs are full of tape read errors. -- Dave White Grass Valley Group, Inc. PHONE: +1 916.478.3052 P.O. Box 1114 Grass Valley, CA 95945 davew@gvgpsa.gvg.tek.com
hurf@batcomputer.tn.cornell.edu (Hurf Sheldon) (10/21/88)
Put a hold on the TK70 order & try one of these.
I was about to order a tk70 to increase backup/restore speed when I happened
on the TD Systems/Exabyte 8mm tape drive combo - cost was $4k Us$ - performance
claims were astounding so I decided with some skepticism to try one.
Wow. 5disk 300 meg dump took 53 mins on 1/6th of a $10 tape vs 3.5hrs on 4
$30 tapes and now the good news - read ahead to the last file on the tape
took 3mins vs 45 for the tk50. The error rate seems about the same, the
controller logic & tape position take a bit longer but once it is rolling
it is fast, and so far very reliable. Installation was the absolute easiest
board plugin I have ever done. The VMS procedure is well documented in the
TD manuals, I would be glad to post the Ultrix/Unix procedures.
I will send you US vendor names if you want - UPS will put it in your
hands in a week.
Hurf Sheldon
Hurf Sheldon Network: hurf@ionvax.tn.cornell.edu
Lab of Plasma Studies Bitnet: hurf@CRNLION
369 Upson Hall, Cornell University, Ithaca, N.Y. 14853 ph:607 255 7267
I sold my Elan, got a job in science; Now, no one takes me seriously.
ps: I haven't tried to boot from this drive yet so you may want to hang onto
the tk50 for distributions etc - we happen to have another system with a
tk50 we can use.
pps;
Tried mail to you with no luck - try sending to me directly so I
can see a return path.
--
Hurf Sheldon Network: hurf@ionvax.tn.cornell.edu
Lab of Plasma Studies Bitnet: hurf@CRNLION
369 Upson Hall, Cornell University, Ithaca, N.Y. 14853 ph:607 255 7267
I sold my Elan, got a job in science; Now, no one takes me seriously.