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Date:      Sat, 30 Jan 1999 08:31:21 +1030
From:      Greg Lehey <grog@lemis.com>
To:        cjclark@home.com
Cc:        BlackshR@fleishman.com, freebsd-questions@FreeBSD.ORG
Subject:   Re: Tape drive
Message-ID:  <19990130083121.K8473@freebie.lemis.com>
In-Reply-To: <199901291501.KAA22170@cc942873-a.ewndsr1.nj.home.com>; from Crist J. Clark on Fri, Jan 29, 1999 at 10:01:36AM -0500
References:  <19990129175337.D8473@freebie.lemis.com> <199901291501.KAA22170@cc942873-a.ewndsr1.nj.home.com>

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On Friday, 29 January 1999 at 10:01:36 -0500, Crist J. Clark wrote:
> Greg Lehey wrote,
>> DDS and Exabyte are just plain too unreliable, though they're getting
>> better.
>
> Greg, is this personal or anecdotal experience? 

Both.

> Or can you point to some references that bear this conclusion out?
> We use Exabyte a _lot_ here at work and hearing this from you
> concerns me. Also, when you say they are unreliable, are you talking
> about the media (properly written tapes fail), the transfer (tapes
> do not get written/read properly), or the hardware (the drives are
> in the shop to much)?

I haven't had much trouble with the tapes (though others make claims
about shortness of life which I can't confirm; I have tapes up to 8
years old which are still just as easy to read as new ones).  The only
problem with tapes, particularly on Exabytes, is that some people use
video grade tape.  I've had new video tapes sent which have lots of
soft errors (in other words, I can read them, but there are lots of
retries).

The basic problem is head wear.  I've had more experience with DDS
drives than with Exabytes, but I've had problems with the latter, and
every DDS drive I have ever had has failed.  The DDS-1 drives (by HP)
all failed within 8 months of moderate use.  The DDS-2 drives survived
up to 2 years.  Considering the cost of the units, I'm seriously
considering swapping to disks.

>> For daily backups, you might consider a small number of large
>> IDE drives.  They'll be fractionally more expensive in the short term,
>> but cheaper in the long run, and they'll certainly back up faster.
>
> The problem I have with this solution is that it seems that you are
> putting all your eggs in one basket. If that backup fails
> catastrophically, you lose _all_ your backups at once.

Like it does if your tape self-destructs.  I wasn't talking of a
single IDE disk, but two alternative ones in a drawer.  Every day you
swap the disk, like I currently swap the tape.

> Seems that you would have to backup your backups occasionally. So,
> you're still stuck with doing tapes or some other media for the
> backup^2.

Yes, it wouldn't be a complete replacement for a tape drive, but it's
the daily backups which place the greatest load on the heads.

> There probably is a procedure to get around this problem (or I may be
> seeing a problem where there is not one), what is the prefered
> procedure for using IDE drives for backup?

There isn't one yet.  I'm still thinking about it.  There may also be
driver problems with replacing disks, but I'm sure we can fix them if
there are.

Greg
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