On Friday 02 May 2014 07:44:05 pm Jim Stewart wrote:
> I believe I've cloned Linux RAIDs by simply using the linux "dd" command on
> the raw RAID device (/dev/md0 for example).
There are two things wrong with this.
1. He said he's not familiar with, or at least hasn't yet used dd.
Even as an "old hand" with dd, ( or maybe because of it ) I'm still
trepiditious whenever approaching dd, especially on "can't lose this" data.
He suggested the possibility of getting if= and of= reversed, which would be
instantly fatal. ( meaning not recoverable )
Don't misunderstand, dd is a wonderful tool, but certainly not the tool
I would choose for this job.
2. Partition table.
Yes, dd will make an exact, bit for bit, copy of the original, but it will not
make a correct partition table for that firmware.
Oh, 3. The array will be off-line for the entire time of the copy.
Depending on the capacity of the device ( since content doesn't matter )
this could be a significant chunk of time.
--
Cowboy
http://cowboy.cwf1.com
Proof techniques #2: Proof by Oddity.
SAMPLE: To prove that horses have an infinite number of legs.
(1) Horses have an even number of legs.
(2) They have two legs in back and fore legs in front.
(3) This makes a total of six legs, which certainly is an odd number of
legs for a horse.
(4) But the only number that is both odd and even is infinity.
(5) Therefore, horses must have an infinite number of legs.
Topics is be covered in future issues include proof by:
Intimidation
Gesticulation (handwaving)
"Try it; it works"
Constipation (I was just sitting there and ...)
Blatant assertion
Changing all the 2's to _n's
Mutual consent
Lack of a counterexample, and
"It stands to reason"
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