Mailinglist Archive: opensuse (924 mails)

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Re: [opensuse] virtual machines great for backups by instant snapshots
  • From: Ted Byers <r.ted.byers@xxxxxxxxx>
  • Date: Sun, 21 Oct 2012 17:03:58 -0400
  • Message-id: <>
On Sun, Oct 21, 2012 at 2:39 PM, Greg Freemyer <greg.freemyer@xxxxxxxxx> wrote:

On Sun, Oct 21, 2012 at 3:30 AM, ellanios82 <ellanios82@xxxxxxxxx> wrote:
Hello SuSErs

Virtual Machines

Could it make sense to PREFER to run Linux as a Virtual Machine??
{ thus, for example, one might install openSuSE 12.2 as ones foundation,
and Next, install a Virtual Machine,
then, Finally install another instance of openSuSE 12.2 on ones Virtual
Machine upon which Virtual Machine
one would do ALL ones work}


best regards

The instant VM snapshots do NOT make redundant copies of the data. Thus

- instant backups protect from user errors, etc.

- do NOT protect from hardware failure

So it depends why you're making backups. I would say many of us worry
about disk failures, etc. For that you need to get your full backup
onto alternate media.

When I first started developing software, my thesis supervisor told me
I should always aim to make my software idiot-proof since I can never
know what kind of idiot is using it. When it comes to statistics,
that could never be more true, given how often I have seen even full
professors recommend the wrong statistical analysis. It takes a lot
of effort to design your software to protect users against innocent
mistakes, but you can't always protect them from 'stupid' syndrome.

But I digress.

It seems to me that such VM snapshots, taken immediately prior to
installing new software (particularly from a source with which one has
limited experience, is a good precaution against installation script
that behave badly (ever seen the chaos wrought by a bad one of
those?). Similarly, taken on a regular basis it serves to protect
against PEBKAC. A colleague of mine protected his team against just
such a thing by configuring automatic backups: a new team member wrote
a badly behaved customer program that not only produced nonsensical
results, it over-wrote the original data which had cost many tens of
millions of dollars to collect (the fool responsible ended up teaching
statistics at a midwestern US college that deserves to be un-named).
When my colleague got a panicked call in the early hours of the
morning while he was on the other side of the planet, he looked at the
results the bozo produced, his program program and made his diagnosis;
and then told his team how to recover the original data from the
backups, and then he did the analysis that the other fellow was
supposed to do but who messed up so badly. he also advised against
trusting the bozo with anything of real value - put him where he can
do no further harm. Had he used a VM snapshot, though, recovery of
the data would have been much, much simpler and faster. That said,
since such a snapshot is just a (very large) file, it can easily be
copied to a CD or DVD (better, multiple such disks, ultimately stored
in different locations)

What would worry me is that someone might get the notion that such a
thing is a magic bullet. As you pointed out, it has both its uses and
limitations, and thus can only be part of a systemati, comprehensive
design, involving multiple elements, such as a decent RAID (perhaps
using hot swappable SSDs, tape or optial backup media, rationally
designed user permissions, redundant servers, &c., &c., &c.

To the OP, I would give a qualified affirmative answer, but advise not
to forget all the many other aspects of security: system, data, &c.


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