About RAID1 and backups

galexios · 28 May 2011

Hi,

So I want to create a foolproof system that will prevent me from losing data in case of a hardware failure, a human error or a virus.

Currently I have 1 TB HD where my OS is installed and two 2TB hard drives set to operate in RAID 1 mode (windows 7's own software raid) where I have my data (music, pics documents and so on).

Now suppose one of my RAID1 hard drives failed, would I be able to access my data from a single drive even without recreating the RAID1 with new hard drive? If I would, then how? I tried to "simulate" hard drive failure by plugging off the SATA cable from one of my RAID1 hard drives, but I wasn't able to access my other drive from windows.

And what if my my OS hard drive failed? Would I be able to put my RAID1 disks into another PC or have a new hard drive and clean install of OS and mount my hard drives into the system without problems? How about recreating the RAID1 configuration again with data already on the drives without losing the data?

I'm thinking of having an external hard drive to which I could backup my RAID1 setup and possibly my OS, but what do you think, would it just be better to stop using RAID1 configuration and use the other hard drive as a backup drive?

Thank you

pparks1 · 28 May 2011

galexios said:

Now suppose one of my RAID1 hard drives failed, would I be able to access my data from a single drive even without recreating the RAID1 with new hard drive?

Yes, with a RAID 1 mirror you can do exactly that.

galexios said:

If I would, then how? I tried to "simulate" hard drive failure by plugging off the SATA cable from one of my RAID1 hard drives, but I wasn't able to access my other drive from windows.

If you have a RAID array, you will see something like a single 2TB D drive. If you unplug 1 drive, the D drive should still be there and you should be able to access it.

galexios said:

And what if my my OS hard drive failed? Would I be able to put my RAID1 disks into another PC or have a new hard drive and clean install of OS and mount my hard drives into the system without problems?

Yes, you should be able to do that.

galexios said:

How about recreating the RAID1 configuration again with data already on the drives without losing the data?

You should be able to do this as well.

galexios said:

I'm thinking of having an external hard drive to which I could backup my RAID1 setup and possibly my OS, but what do you think, would it just be better to stop using RAID1 configuration and use the other hard drive as a backup drive?

You NEVER want to consider RAID a backup. If I were going to use RAID1, I would use it on my OS. This way, if 1 drive failed, I could still boot the system from the other drive and keep going.

No matter what type of RAID you use, you ALWAYS need to BACKUP your data. RAID is not a backup. For example, even with a RAID1 system in place, lets say that you do something dumb and you highlight your data, accidentally delete it all and then empty the recycle bin. Well, it disappeared from both drives. It's gone. Let's say you get a virus and it wipes out data, well it just wiped out data on both drives.

Instead of doing a RAID1 mirror, I would suggest instead having 2 standalone drives, and run a job that synchronizes data between the 2 drives every 2-4 hours. This way you have a window from accidentally deleting something to pulling it back from your backup drive. And this eliminates and concern of being able to move the drives and place them into another computer and being able to see the data.

RAID is not a backup.

galexios · 28 May 2011

If you have a RAID array, you will see something like a single 2TB D drive. If you unplug 1 drive, the D drive should still be there and you should be able to access it.

That is how I thought it should work, but when i unplugged other of the two hard drives in RAID1, there was no drive visible at all in the My Computer, even though the other drive was still attached. When I reconnected the drive, then the RAID1 drive became visible and worked normally.

From the disk management utility I saw that the other drive was still connected, but it didn't show up so that I could have accessed the files on it.

Instead of doing a RAID1 mirror, I would suggest instead having 2 standalone drives, and run a job that synchronizes data between the 2 drives every 2-4 hours. This way you have a window from accidentally deleting something to pulling it back from your backup drive. And this eliminates and concern of being able to move the drives and place them into another computer and being able to see the data.

That is exactly what I meant. Since the possible downtime caused by a hard drive failure is not that big of a problem for me, maybe the RAID1 is not the best way to go. Could you suggest any good program/s to do the synchronization? Should it be just a simple cloned drive or would it be better to have a some kind of incremental backup on the other drive? For incremental backup, is windows 7's own backup utility any good, or do you think that some 3rd party application would be better?

But first I would need to be able to disable the RAID1 configuration so that my data would be safe on the other drive, after which I could setup the backup system.

pparks1 · 28 May 2011

I use robocopy which is simply a command line driven tool. Syntax looks like following
robocopy D:\downloads G:\backups\downloads\ /mir

The /mir at the end says to mirror the source and destination. Thus, if I delete it from D:\downloads, the next time robocopy runs it will also delete it from G:.

You can also use graphical utilities like sync toy (from MS) or Karen's File Replicator (free).

The only reservation I have with backup software, is that it makes an image file. So, if you don't have the software, you often cannot get into the backup. That is the reason that I often times opt for a straight up copy of the file on the backup drive. This way, I don't need anything to get at the data.