[DM-MUG] backups, external FW drives, and concatenated RAID

[Bryan Baker]

You might also be able to use another RAID feature to mirror the 500  
to the 250's. Not too sure if that'd work right though.

RAID 0 = Striping - Faster, but no redundancy, so loss of 1 drive is  
catastrophic.
RAID 1 = Mirroring - As the name implies 1 (or more) drives mirror  
the other - 100% redundant, but you loose capacity.
RIAD 5 = Striping with parity - common, but popularity is fading,  
more reliable than 0, but less than 1.

There are lots of other permutations and variations, but those are  
some of the more common.


On Mar 27, 2007, at 8:54 AM, Darcy Baston wrote:
> Sure!
>
> Here's what my archive setup was before:
>
> 1 Firewire HD 250GB (in use)
> 1 Firewire HD 250GB (backup of other)
>
> Here's what I have now
>
> 1 Firewire HD 500GB (in use, what I bought just recently)
> 1 RAID  (1 Firewire HD 250GB + 1 Firewire HD 250GB) = 500GB, mounts  
> on desktop as one HD of 500GB (backup of other)
>
>
> Using the RAID features of Disk Utility, I told it to add the 250GB  
> capacity of one of the drives to the end of the 250th gigabyte  
> (relatively speaking) of the other, and mount it on the desktop as  
> one single 500GB drive. It's an illusion that there is one drive of  
> 500GB, when it's really just 2 drives of 250GB each.  
> "Concatenation" means "put the space of one at the end of the other  
> so when one fills up, spill over to the other, but only ever show  
> me one drive icon/device".
>
> That gave me a new pseudo 500GB drive. That left me with just one  
> device, and no backup drive for that new higher capacity pseudo  
> device, so I bought an external single 500GB drive. The new 500GB  
> single unit is the one I'm now using as the archive, and the RAID  
> Concatenated setup is the backup.
>
> This means I have 3 external hard drives. I'd love to go back to  
> two. If anybody wants to buy the 2x250GB drives, I'll gladly use  
> the money to put towards another single 500GB drive. :) They're  
> only 6 months old if anyone's interested.
>
> Darcy
>
> On Tuesday, March 27, 2007, at 06:57AM, "Victoria L. Herring"  
> <lists at herringlaw.com> wrote:
>>> I ran out of room on my external 250GB Archive drives (one source,
>>> one backup) this weekend. So I bought a new external 500GB WD MyBook
>>> Firewire drive, and used OS X's Disk Utility RAID features to
>>> concatenate the two 250GB externals to act as the 500GB backup
>>> solution for the new 500GB drive.
>>
>> Darcy I really hate to sound stupid, and it IS early, but perhaps you
>> could explain to me what the value of a RAID is and what
>> concatenation is and why this is better than the two source and
>> backup drive system you had....the picture was a big help but I'm
>> missing some of the early explanation....
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