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RAID 1, 4 disk array, disaster recovery possibilities?

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Oscar Janicki
RAID 1, 4 disk array, disaster recovery possibilities?
on May 20, 2011 at 9:45:48 pm

Hello everyone. First post! I'm an IT consultant with a thought about an interesting use of RAID in my personal network, and I wanted to get some feedback.

I'm building a backup server for my home network. As I understand, if I use 4 drives in a RAID 1 config, then purposefully remove one drive and store it offsite, the array will degrade but will rebuild if I insert the exact drive back.

Now, if I take this a step further, if I lose the other three drives, is there enough information left on the drive to rebuild the array if it was installed into a new computer with as much of the same hardware as possible, including the same RAID controller?

Because of my lab environment, I have several TB of data that needs to be backed up, and I'm trying to learn to live without tape backup. Any other thoughts for economical on/offsite backup on a home network?


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Alex Gerulaitis
Re: RAID 1, 4 disk array, disaster recovery possibilities?
on May 21, 2011 at 2:39:07 am

4-drive RAID1 array? Meaning the info from one drive is mirrored, duplicated to the other three?

I haven't heard of RAID1 configurations with more than 2 drives although it's not impossible - just unusual. If that's indeed the case - then yes, you can take one of the drives off-site (unmount first) and you will be able to restore the contents of the array if something happens to the other three.

Alex (DV411)


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Bob Zelin
Re: RAID 1, 4 disk array, disaster recovery possibilities?
on May 21, 2011 at 5:53:42 pm

come on Oscar, you are not an IT consultant. But your questions are ok.

I'm building a backup server for my home network. As I understand, if I use 4 drives in a RAID 1 config, then purposefully remove one drive and store it offsite, the array will degrade but will rebuild if I insert the exact drive back.

REPLY - this is incorrect. RAID 1 is called Disk Mirroring. You use a single drive, or a group of drive to create a duplicate, or a mirror of the other set. You can't compress all the redundant data from the drives onto one drive, and then "take it home". The idea of having all the data compressed onto one drive (called a Parity drive) is called RAID 3 - which was well used by companies like Medea and HUGE systems, but is never used anymore. And no one just took out the parity drive - it was there at all times to be your emergency, in case you had a drive failure.



Now, if I take this a step further, if I lose the other three drives, is there enough information left on the drive to rebuild the array if it was installed into a new computer with as much of the same hardware as possible, including the same RAID controller?

REPLY - no, no, no. If you want to "take home" a drive with the identical information, buy a second drive array, and use a clone program (like super duper) to make a clone of your media. You don't
intentionally "break" your drive array to keep it as a backup. Drives are so damn cheap today, and there are so many cloning programs out there. Your concept of what you want to do is rediculous.


Because of my lab environment, I have several TB of data that needs to be backed up, and I'm trying to learn to live without tape backup. Any other thoughts for economical on/offsite backup on a home network?

REPLY - a 1TB drive is $55 bucks. Buy a SATA drive toaster for $29 bucks (that connects via SATA or USB) and make a backup. You don't need LTO for what you are doing. There is a new invention called GOOGLE that will let you easily find countless numbers of backup programs - some free, some inexpensive. And you can always simply drag your media from one disk to the other, and don't spend any money.

Bob Zelin



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Chuma Dyasi
Re: RAID 1, 4 disk array, disaster recovery possibilities?
on May 13, 2013 at 1:08:31 pm

Good day Bob

You seem like a smart guy, I am currently busy trying to do an audit of our current disaster recovery plan, now I just want to find out from you, what methods or new technologies can we use in order to minimise our RTO (Recovery Time Objective)? We currently standing at about 3 days

Regards

Chuma, South Africa


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