[DM-MUG] Using RAID with Tiger

[AB]

As I understand it...
RAID Mirrored mirrors the contents and files of a single drive in the event that drive fails—see excerpts from the info Jon gave.
RAID Stripped takes content and distributes it across multiple drives. Kind of like putting multiple support beams in. Each hard drive is a support beam and collectively behave as one unit. One of those drives failing won't necessarily have detrimental repercussions. I believe John Thompson gave a detailed description. Though I might be confused on this. 

As far as erasing contents on the existing drive, I'm not sure and was wondering the same thing myself.

Here's what I saved for reference on what was mentioned before about RAID. I thought there was another detailed summary, Jon gave, but I this seems to be all I saved.

Jon Thompson wrote this on May 19, 2009:

1) A good backup is a verifiable backup
If you are dumping info into Time Machine,
and you are _never_ pulling info back out of it and checking, how do
you know that the data is good? In the instance of the SideKick data,
this means that they would have known that the backup is good, and that
they could rely on it. Until you know that you can recover from it, you
cannot call it a good backup.
2) A good backup consists of many backups of the same data.
I
store three months of backups, and I consider that too little, but
don't dare increase my budget. If you are relying on all of your data
being on a single hard drive, what happens if there is a fire and both
your computer and backup is lost? If all of your backup is in one cloud
(Mozy) and that cloud bursts like the SideKick cloud did, you are
hosed. Now, if you have daily backups on a time machine volume, and a
weekly backup to Mozy, you are protected from either example. Mozy is
your offsite backup, the time machine 
3) Synchronization is not backup.
Synchronization
ensures that all of you data is the same between all instances that you
create. If you are syncing your address book on your mac with an
iPhone, you have two instances of the data, but they are tied together.
If you delete a contact on one (or a virus deletes all of them) that
deletion is transferred to your backup. I realize that there are ways
that the sync service tries to reduce the chance of this, but it is
still a possibility. However, an offline copy of your address book on a
USB thumb drive that is not plugged into your computer cannot not be
changed, at least until it is plugged in again. Dropbox is a
synchronization service.
4) RAID is not backup.
RAID
(except 0) is a way to protect from hard drive crashes. It does not
protect from application corruption, accidental deletion, or
intentional deletion. All of which are much more likely than hard drive
corruption during the majority of the life of a hard drive. RAID is
useful for server admins that deal with distributing data amongst many
hard drives, which actually is a great way to exponentially increase the likelihood of data loss due to hard drive failure.
RAID
0 offers no protection at all- in fact, it is will exponentially
increase your likelihood of data loss due to hard drive failure. Be
careful when purchasing large external hard drive, as they are sometimes two drives that are internally configured as RAID 0. This is useful for professional video primarily.
5) Backup as sparse as you are willing to recover from.
- If you couldn't stand losing more than a week's worth of data, you'd best be backing up weekly.- If you couldn't stand losing more than a day's worth of data, you'd best be backing up daily.- If you couldn't stand losing more than an hour's worth of data, you'd best be backing up hourly. 
You know what is important and what is not. Make sure to taylor your backup routine to your needs. Incremental backups, such as Time Machine are good about this.


--- On Sun, 11/29/09, John Robertson <john at createmydvd.com> wrote:

From: John Robertson <john at createmydvd.com>
Subject: [DM-MUG] Using RAID with Tiger
To: "Des Moines Mac Users Group" <dmmug at dmmug.org>
Date: Sunday, November 29, 2009, 11:52 AM

Just wondering if anyone has any experience using RAID on a single  
user OS.  I purchased a new 1TB drive and I was thinking of  
partitioning it to use as a mirror for my 500G drive.  I have two  
questions before I attempt this. The 1st question is, will it erase  
the contents of the old drive (the 500 gig) that I am adding the 1TB  
to when I turn on RAID? Also, what are the differences between RAID  
mirrored and RAID Striped? I understand how Mirroring works and a  
little about RAID 5 (which is only available on servers) but I don't  
know which of the other option available here would be better to use.

Thanks,
    John

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