What is a RAID?

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Jeff
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What is a RAID?

Post by Jeff »

I am looking to convert my harddrives to back up each other automatically. Is this possible with a RAID? Or should I use a software app to make them backup.

I am looking for something that does it automatically and doesn't mind if i don't leave my computer on all of the time.

Also, is their something you need in your hardware to make a RAID?


Thanks for your answers.

Jeff

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Post by Andy »

Software is in my opinion better because RAID can have issues. Id use Norton ghost or a similar program to backup your data.

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RAID

Post by RentedMule »

Use RAID mirroring. One drive fails, the other takes its place automatically. Then you pop in a relpacement, rebuild, and your back to having your mirror.

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Post by Andy »

Thats the issue I find with RAID. If the drive fails, yes the data is still there, but the system will no longer work until you fit a new drive and rebuild it. And often you cannot rebuild it from the experiences Ive heard from people. So, infact its even more unreliable.

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Post by empireum »

If the drive fails, yes the data is still there, but the system will no longer work until you fit a new drive and rebuild it
I don't quite get this. If a drive in a mirriring RAID (which does not replace a backup solution!) fails, the system will continue to work and display an appropriate warning. That's what I thought and my mirrored RAID systems (nothing fancy, done entirely in softare or on some cheap PCI cards) always worked like that. The system never stopped working after one drive went out...

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Post by Andy »

It will continue to work as long as the system doesnt crash. Once it crashes you need to rebuild the RAID array with a new drive, at least thats what a friend of mine told me when one of his drives failed.

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Post by empireum »

You mean the array has to be rebuilt if the system needs to be restarted, right? My (cheap) RAID controllers nagged me with warnings on boot if one drive of the array failed, but the data has always been accessible...

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Post by Andy »

Thats what I meant yes. I guess yours were better built and worked anyway.

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Post by empireum »

Well, don't know exactly. I'm just telling what I'd experienced. But I certainly don't want to get into an argument with you

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Post by Andy »

I didnt intend to argue, just doing the same as you, telling my experiences. But in my opinion RAID is best avioded where you can.

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Post by empireum »

Well, I don't mind using a RAID-0 for faster access to the data (i.e. as a scratch disk or something like that), but I'd never ever put any important data on a RAID-0. I'd use RAID-1 or -5 for that. As said, my experience with RAID has been rather good, I'm sorry it didn't work out for you.

I agree with another point: Nothing beats a good backup.

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Post by Jeff »

What is a RAID-0? Or Another number after that? I'm pretty new to this concept.
-Jeff

RentedMule
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Raid Numbers

Post by RentedMule »

Linear Raid = You "append" drives to one another. When Drive one in full, drive 2 is used, like one big linear hard drive

Raid 0 = Stippong. Each drive is used in unison as a single drive. Every other packet it written to each hard drive improving read/write performance.

Raid-1 = Mirroring. One drive is used and the other is an exact copy. When one goes down, the other takes over.

Raid 5 = Parity. Several drives are used in a striping mechanism and one or more drives contain parity information. When the main drive goes down, you haveto rebuild the main drive from the parity drives.

Raid 10 = Raid 0 + Raid 1

Raid 15 = Raid 1 + raid 5

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Post by empireum »

Good explanation. Just to add there's also

RAID 50 = RAID 5 + RAID 0

and RAID 2, 3, 4 and 6, IIRC. But I don't have their definitions at hand right now.

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Post by Jeff »

thanks for those, that gives me a better understanding.

The type I want is RAID-1
-Jeff

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Post by empireum »

OK, but please remember that RAID-1 does not replace a working backup solution. If a file on a RAID-1 drive/volume is accidentally deleted or your system gets hosed by a virus, the damage will simultaneously occur on the 2nd drive, too. The only event a RAID-1 will protect against is hard drive failure. RAID 1 is no backup.

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Post by Jeff »

That's okay, I only want it for hard drive failure purpouses... or do I?

Hmm have to think about that (I guess the purchase of an external hdd would fix that problem though).
-Jeff

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