[SAGE-AU] Re: [Talk] Reality check...

[Greg 'groggy' Lehey]

On Wednesday, 11 September 2002 at 15:30:20 +1000, John Stern wrote:
> Daniel O'Connor wrote:
>>> IDEA:
>>> The cost of DLT & LTO tape media is ~$3/Gb.
>>> The cost of commodity IDE drives is ~$1-2/Gb.  IDE enclosures with
>>> either Firewire or USB are cheap & readily available.
>>
>> IDE costs around $3/Gb too.
>
> 9940's (60GB) cost about $240 an 80GB seagate is ~$210.
> I don't know the pricing on LTO or DLT.

Everybody so far has compared only purchase prices.  In my experience,
tape drives are by far the most unreliable part of a computer system,
and order of magnitude more unreliable.  18 months ago I had,
connected to my system, 

 - An AIWA DDS-2 drive.
 - A Sony DDS-4 drive.
 - An Exabyte 9700.
 - A Quantum DLT 4000.

The Exabyte died about 15 months ago.  The DLT drive, which I didn't
use much, still works some of the time, but it tends to get confused
with long files.  The AIWA doesn't get used much, and I think it still
works.  The Sony died, conveniently, the day after a disk drive backed
up to it died, so I can't get at the backup.  None of these drives
cost less than $1000.  If anybody knows a reliable place to get the
Exabyte and Quantum drives repaired, I'd be grateful.

> Though good old DAT isn't such a bad alternative at the low end of the
> scale.
> Tape is a linear media and as such is very fast to write to.
> Typically much faster than disk..

My experience doesn't bear this out.  Before changing to IDE, my
backups took up to 8 hours a day (sequential from multiple systems on
the network).  Now they're all done within an hour.

Top end tape drives may exceed the transfer rate of IDE drives, but
the ones I'm talking about don't even come close.  The DDS-4 drive
does about 2 to 3 MB/s, the DLT about 4.  By comparison, the Western
Digital drives which I replaced them with will do about 35 MB/s.  A
5400 rpm drive may make only 25 MB/s, but it's still much faster than
tapes.

Greg
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