Xref: utzoo comp.os.vms:9445 comp.sys.dec:826
Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!cornell!uw-beaver!tektronix!gvgpsa!davew
From: davew@gvgpsa.GVG.TEK.COM (David C. White)
Newsgroups: comp.os.vms,comp.sys.dec
Subject: Re: Error count on TK50s
Keywords: TK50
Message-ID: <1040@gvgpsa.GVG.TEK.COM>
Date: 19 Oct 88 02:48:18 GMT
References: <654@prlhp1.prl.philips.co.uk>
Reply-To: davew@gvgpsa.GVG.TEK.COM (David C. White)
Organization: Grass Valley Group, Inc., Grass Valley, CA
Lines: 42

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