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

[Ray Bowler]

I'm trying to remember but don't the two drives in the RAID have to 
be the same size?

At 10:29 AM -0500 3/27/07, Bryan Baker wrote:
>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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>
>--
>Bryan "ka-klick" Baker
>Singer/Songwriter
>With 2 New CDs!!! See my website for details
>kaklick_mar... at mac.comhttp://ka-klick.com
>
>
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-- 
Ray Bowler

rbowler.home.mchsi.com