Re: [tlug] Setting up a RAID 1 with Ubuntu (Was: Hard Drive Failure)

[Edward Middleton <emiddleton@example.com>]

Dave M G wrote:
 >> You don't *need* identical drives, the point was that it doesn't make
>> much sense deliberately buying drives from different manufacturers.
> Okay... but can I have slightly different drives? Like, assuming both
> are SATA, 7200 rpm, and 3Gb transfer speed, but one is 450 MB, and the
> other is 500 MB, can I still set them up as a RAID? From what others
> have said, the answer is yes, though of course the size of the RAID
> would be constrained to the smaller of the two drives.

Yes, you can as far as I can tell even have the ridiculous RAID1 with
two partitions on the same drive ;)

>> You are talking about the merits of backup versus raid.  This is pretty
>> analogous to ABS breaks(raid) and airbags(backup).  ABS might stop you
>> having an accident, airbags will lessen the impact. 
> 
> That analogy confuses me. How does having a RAID stop me from having
> drives fail? I thought the whole point was that if one of the two RAID
> drives failed, then I could just replace it, and the still-working RAID
> drive would copy all the data over to it. So isn't that another form of
> back up, not prevention?

Well its analogy, yes there are differences.  Look at it this way,  if a
RAID1 drive fails, its a mater of inconvenience (i.e. replacing the
failed drive), if your standard drive dies its a matter of loss (i.e.
whatever has changed since your last backup).

There are also the more practical issues like, if a RAID1 drive fails
all things being equal you can continue to use the machine until you
have time to get a new drive.  If you have a catastrophic disk failure
you have to fix it before you can do anything.

The catch with RAID1 is that it will not protect you from self inflicted
errors like overwriting or deleting files.

Edward