>> If you don't need high performance, and you don't want to buy a
>> spare card in case the 3ware card dies, you might want to consider
>> raidframe.  Otherwise, [you're] just adding a new single point of
>> failure into your systems.

Not *just*.

As compared to no RAID at all, you're gaining a significant uptime
benefit, especially if you have spare drives on hand and a hot-plug
backplane.

As compared to RAIDframe, you are adding another CPU, which is an
uptime lose, as compared to offloading the RAID processing, which is a
win in various ways (such as being able to boot off RAID 5, such as
greatly reduced chance of data corruption if the host OS crashes, such
as a (relatively slight) performance increase, to name just three).
Which wins depends on how the reliability characteristics of the
additional CPU compare to those of the drives - will you win more on
uptime from RAID redundancy than you lose from the additional CPU
failures?  In most cases, especially given modern drives' MTBFs as
compared to no-moving-parts hardware, it's a win.

> spending little bit less money for backup system, or very little
> money for somehow smarter backup system is much better solution.

Better solution to what?

RAID provides robustness in the face of drive failure.  (I'm ignoring
RAID 0, which provides nothing but performance gains and sometimes not
even that.)  Backups, when done suitably, can provide some of the same
robustness in terms of (lack of) data loss, but not in terms of uptime.

> but ONLY backup is really good if backup media is physically
> disconnected after usage - or it is almost no protection at all.

Again, protection against what?  Online backups *are* protection
against some things, enough to be worth doing in some environments.

> disc failures are not more probable than software failure, other
> hardware failure (transmitting bad data through bus), security
> compromise etc.

In some cases they are.  In some cases those other threats are dealt
with in other ways - or are not dealt with; either way, it can still be
worth defending against drive death per se.  I do, for example, and
I've had two drive failures that I didn't lose any data to, thanks to
what I have in place.  (Not really RAID, but similar in terms of the
threat model.)

> only true backup with media disconnected after usage means some real
> security,

Against what?  You seem to have a very limited threat model - and, more
of a problem, you seem to assume everyone should share it.

> while all RAIDs are in most (not all) cases pure waste of money.

How nice of you to concede that perhaps a few of those people spending
money on RAID might actually know what they're doing.

Perhaps they just know their threat models better than you do.

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