[Discuss] SSD drives vs. Mechanical drives

[kentborg at borg.org (Kent Borg)]

On 05/05/2014 03:50 PM, Richard Pieri wrote:
> Repeat after me: redundant disks do not provide data integrity. 

No, you are not my kindergarten teacher.

And "data integrity" isn't as narrow and simple a definition as you pretend.

> Redundant disks -- be they rotating platters or flash chips -- will 
> keep the system running if one fails but they won't protect your data 
> from corruption or loss. 

Depends on what I mean by "corruption or loss".

Scenario 1: Horrible noise comes from one disk and it quits working.
Desire: Go back in time to just before the horrible noise.
Solution: RAID works great, in fact you are already forward of point and 
still running. (Order a new disk.)

Scenario 2: Horrible bug scribbles all over your data.
Desire: Go back to before the scribble.
Solution: Pull out your recovery plan (you have one, of course) and 
start the recovery process.

The two cases are different. To backup your data you need to understand 
why you have your data and what could go wrong with it. And to think 
through how you can prepare in advance. If hypothetical someone thinks 
that RAID handles case #2, then that person is not a good person to 
think through the problem. When you repeat slogans about what RAID can't 
do, I think you are talking to that same hypothetical person. I don't 
think that hypothetical person is here.

-kb