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RAID 1 as data backup question

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July 30, 2007 7:45:12 AM

I'm going to build a Windows Home Server PC out of an old PC. I'm wondering if I setup the drives as BIOS level RAID 1 would I be able to swap out a hard drive easly if a single drive should fail, or should I be using something other than BIOS level RAID 1 in order to easly swap out a drive?
a c 377 G Storage
August 2, 2007 3:12:42 AM

RAID 1 will save you from a failed drive. Replace the failed drive and tell it to rebuild the array. RAID 1 is not a "backup". It will not save you from viruses, accidental file deletions, or crappy drivers.
August 25, 2007 5:46:46 PM

Hawkeye22 said:
RAID 1 will save you from a failed drive. Replace the failed drive and tell it to rebuild the array. RAID 1 is not a "backup". It will not save you from viruses, accidental file deletions, or crappy drivers.


The part where you say RAID 1 is not a backup, I beg to differ. RAID 1 is a mirroring array, the same data goes on both drives. If one drive fails the exact same data is on the other drive. This is a step in insuring your data. I have built a few mirroring array systems for small businesses and then a external hard drive or a zip drive to add a little more insurance.

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a b G Storage
August 25, 2007 6:11:50 PM

RAID 1 is NOT a backup.
If you incurr a major OS error, virus, or any other software malady, it is mirrored to other drive also at precisely the same time.
RAID 1 will provide protection in the event of a hard drive failure , that is all it will do. But do not for 1 minute believe that it is the same as a backup.
August 25, 2007 6:14:04 PM

ULTRA_AMD said:
The part where you say RAID 1 is not a backup, I beg to differ. RAID 1 is a mirroring array, the same data goes on both drives. If one drive fails the exact same data is on the other drive. This is a step in insuring your data. I have built a few mirroring array systems for small businesses and then a external hard drive or a zip drive to add a little more insurance.


Read his post again, he is absolutely correct. RAID is not a substitute for backup. Yes, both RAID and backup protect your data, but do so in ways that protect from different failure modes.

RAID's primary purpose is availability - the ability to keep a server running during and throughout a storage system hardware failure. If a hard drive fails in a RAID-protected system, the system continues to run with the failed drive. Replacing the failed drive restores the redundancy, and the server keeps running throughout. This is the failure mode that RAID is designed to protect against.

A backup is not targeted at availability - if a server that is backed up but not in a RAID configuration goes down, it's down. No one can access it or it's services. Replace the failed component, and if that's the hard drive, then you restore your data from your backup. Now the server can be brought online again just like it was.

But backup can protect against many failure modes that RAID is ineffective against. If a virus infects your system and corrupts Windows to the point where the server won't boot, RAID doesn't help you. The second drive in the RAID 1 is a mirror - it's infected, too. If a user who's accessing the file server deletes a whole folder full of data on accident, guess what? It's deleted from the other RAID drive, too. RAID can't save you here. The only thing that can save you now is a backup.

Backup involves point-in-time snapshots of data. This means that you can restore data from backup that's a day old, a week old, a month old, etc. RAID is real-time -- there is no going back to old copies of data.

RAID also doesn't protect against a site catastrophe. If your building catches fire, your whole server is ruined, and the data along with it. If you have an off-site backup of the data, it's just a matter of calling your server vendor, ordering a new server, setting it up, and doing a restore. Back up and running.

So, do not confuse RAID and backup. They both play a part in protecting your data, but protect it from different things in different ways.
August 25, 2007 6:27:02 PM

What SomeJoe said. Also it is my understanding that at least some RAID1 implementations still rely on metadata and thus the data may be lost if migrated to a different system. Please correct me if that is wrong.
January 6, 2010 11:52:10 AM

I run W7 Ultimate. I have a 1Tg and a 180g discs in a ab external net storage up and running RAID1. Also installed 57xxSteelvine Manager. The backup/mirror was set up in the 2 disc and verified. I am now confused. Understood that my whole disc including OS had been mirrored on both external drives so that if my drive in my computer crashes I can use an external to recover everything. Also that any data added on computer is automatically (incrementally?) loaded on the external drives. Does this not happen and is this not an effective backup.
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