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

[David McDonald]

> -----Original Message-----
> From: Greg 'groggy' Lehey [mailto:Greg.Lehey at auug.org.au]
> Sent: Friday, 13 September 2002 12:08 pm
> To: John Stern
> Cc: Daniel O'Connor; talk auug; sage-au; acs canberra
> Subject: Re: [SAGE-AU] Re: [Talk] Reality check...

> > 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.

I'll second that. The fastest tape drives in general circulation that I am
familiar with operate at around 6 Mbytes/s (maximum). You can typically
sequentially access a disk faster than that (probably even a very old ide
drive). Most tape drives don't operate at anywhere near sequential raw
partition (sorry Greg, that should read "slice") speeds.

On top of that, many backup applications spool to disk first (this can be
good when backing up many small files), but even if the tape drive is faster
than file system I/O, the chances are that the data will go no faster than
the disk file system will allow. (So I don't think that speed should be the
primary consideration unless you have a backup system that can make good use
of it).

I've also seen comments about reliability of tape vs. disk in transit. Some
have complained about dropped DLT tapes. There some types that are even
worse (read as "all types that have an aluminium base"). 2.5" drives
(designed for laptops) are typically quite robust (in disk drive terms) and
if they are suitably padded in a case should be extremely robust - quite
likely better than many tapes (particularly as cartridge tape housings are a
fairly integral part of the tape). As for static - static can damage tape
too. Again it comes down to the housing.

We just need some nice manufacturer to package these up in a pretty box that
a manager would buy. ;^)

My suggestion is if you want to transport disk drives regularly, drop in at
one of the many electronic hobbyist stores and get yourself a strong case
with foam rubber padding. Put your drives in anti-static bags (the ones that
many electronic components such as disk drives come in) and you have
yourself a fairly sturdy and reliable transportation mechanism.

As for offsite storage; I haven't asked, but I cannot imagine that offsite
tape storage companies would object to handling disks for you - after all,
they handle the tapes "by hand" anyway. The security of these sites is
typically as good as most organisations have for their own computer rooms
(or better) and a worthwhile one will have expensive fire suppression and
environmental control too.

Regards,

Dave McDonald

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