Software RAID 1, or "Mirroring", makes an exact copy of all the data between two disks. So, when one of the drives fails - because HDD failure is a matter of time - all data is safe on the other disk. Let's create a software RAID 1 in Windows 7.
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To create software RAID 1 with Windows 7, we will need two hard disk drives - preferably of the same size - and at least Windows 7 Professional or Windows 7 Ultimate.
We can't create a software RAID 1 in Windows 7 Home Premium
Software RAID in Windows 7 is nothing less than a mess. Different Windows 7 versions have arbitrary restrictions on which RAID levels they allow us to create.
If we bought a PC with pre-installed Windows 7, we probably have Windows 7 Home Premium. That means that software RAID 1 is out of reach.
Due to licensing reasons, on Windows 7 Home Premium we can only create a RAID 0, "Striping", which is a useless type of RAID for data security.
When one disk fails in the RAID 0, all the data from all the disks is lost, permanently and without any chance of recovery.
The "Spanned Volume" option isn't even RAID. It's a JBOD array (Just a Bunch of Disks), where two or more disks appear as a single large disk. But this too doesn't offer any data security, when one disk is lost, all the data from every disk in the array is lost.
So, we won't be covering either scenario in Windows 7 Home Premium.
Why software RAID 1 and not software RAID 5?
For the same arbitrary licensing reasons, software RAID 5 is completely off-limits to any version of Windows 7.
We will find the option by right-clicking on the drive, but it will always be grayed-out, just taunting us with what it would be...
Only Windows Server editions - as old as Windows 2000 server - can create a software RAID 5.
With RAID 0 being useless for data security and RAID 5 being unavailable, creating a software RAID 1 in Windows 7 is the only viable option.
How to create a software RAID 1 in Windows 7
As we mentioned earlier, on a level 1 RAID two disks have the exact copy of all the data at any single moment. So, when one of them fails, the data is safe on the other.
The downside of RAID 1 is that we lose 50% of the total disk capacity. If we use two 1TB disks for RAID 1, the array will have a 1TB capacity in total.
To create the software RAID, we press the Windows key + R, to open the "Run" dialogue, and type:
Creating a software RAID 1 with brand new disks
If both of the disks we will use for the Software RAID 1 are brand new, once we open the Disc Management console, we will get a message to initialize the disks.
If the disks are smaller than 2TB each, the MBR partition style is good enough. Else, we need to select the GPT partition style.
After that, we right-click on one of the two unallocated volumes, and select "New Mirrored Volume...".
On the New Mirrored Volume Wizard, we add the 2nd disk...
...which will allow us to move forward.
In theory, we can have more than two disks in a RAID 1 array, but they will all be copies of one disk, and a terrible waste of space. Four 1TB disks in RAID 1 give us a 1TB array, with 75% of the total capacity lost.
Finally, we assign a drive letter to the new array...
...and format it to NTFS.
The system warns us that this operation will convert basic disks to dynamic. The only downside of that is that we can't dual-boot another operating system from a dynamic disk e.g. a Linux distribution or another version of Windows.
By choosing "Yes", our Software RAID 1 in Windows 7 is ready.
We will find it in the "Computer", as a single disk.
Creating a Software RAID 1 copy of an existing data disk or partition
Let's say we didn't buy two more disks but had already a disk or partition containing our data, and bought another disk to create a RAID 1.
In this case, we right-click the NTFS volume and select "Add Mirror...".
The system will show us the new disk, and we click on Add Mirror.
Both the disk we already had and the new disk will be converted to dynamic disks.
The software RAID 1 is created and starts resynching.
As you can see, the original data we had on the single disk isn't lost, and we have complete access to it while the RAID is resynching.
It's best to leave the RAID 1 resynching complete before we do any intensive writing or deleting of data. It is a strenuous procedure for the disks, and we shouldn't make it any harder. Disks are known to have failed during the RAID resynching.
Creating a Software RAID 1 for the Windows installation
Since we don't need to format both drives to create Software RAID 1, we can also create a RAID 1 with the Windows installation. But we shouldn't do this if we wish to dual-boot with another operating system, because of the dynamic disk restrictions we mentioned earlier.
We just need to mirror both the System Reserved partition...
...and the C: partition.
Mind you that if, for some reason, we don't have a "System Reserved" partition, it's impossible to create a bootable software RAID 1, the option will be grayed out.
Now, on each system startup, we will get two boot options, one for each disk.
Both installations are identical, so it doesn't matter if we choose the "secondary plex" one.
What happens when one disk fails in RAID 1
When one of the hard drives does fail, we get a "Failed Redundancy" message at the Disk Management console.
We still have complete access to our data, and nothing is lost provided the other disk still works properly.
Unfortunately, the system doesn't give us any warning whatsoever that one of the disks has failed.
This is a huge oversight, especially if we consider that a Linux Software RAID can send us an email as soon as a disk fails. But that's Microsoft for you.
We must make a habit of checking ourselves the Disk Management console every once in a while, to make sure that RAID 1 is working with both disks and full redundancy.
If we have the Windows installation on RAID 1 and lose the original disk, we will just get a cryptic message when trying to start the plain Windows 7 option.
In this case, we need to reset and choose the secondary plex.
How to fix a collapsed software RAID 1
We must replace the HDD that has failed with a new one, as soon as possible.
Then, before we remake the array, we take a complete backup of any essential data from the working disk, preferably on an external hard drive.
The last thing we want is for the only working disk also to crash while rebuilding the array.
After we have backed up our data, we remove the mirror...
...making sure we have selected the Missing disk...
After that, the missing disk entry will disappear, and we can create the RAID with the new hard drive.
Why choose the Software RAID 1 instead of the motherboards "hardware" RAID?
Most current motherboards boast their RAID controller.
Many users think of this as a "hardware" RAID, and thus a better solution than a software RAID 1 or software RAID 5.
The thing is that motherboard RAID isn't hardware RAID. It is software RAID, run by the BIOS and the Windows drivers.
It's a worse solution than both true software and true hardware RAID, and that is why it is known as Fake RAID. You can read about it in the linked article.
The fact is that we need an expensive hardware RAID controller - upwards of $300-$400 - to get true hardware RAID. Some cheap PCI or PCI-E controllers also use Fake RAID.
All in all, software RAID 1 in Windows 7 is far from perfect, but it is the best way to get RAID 1 on our Windows 7 PC, without paying through the nose for it.
Did you have any trouble creating a software RAID 1?
If anything didn't work for you as described, leave us a comment.
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