Windows Server - Build a software RAID-5 with only 2 drives (temporarily)?

So, I've run into a conundrum, and I'm not sure how to go about fixing it!

Previously, I had a RAID-1 setup on my Windows Server, that was happily RAID'ing 2x2TB drives using Windows' software RAID. Fast forward to a few weeks ago, an I ended up purchasing another 2TB drive. Now, I'm looking to migrate my RAID-1 setup into a RAID-5 setup, effectively doubling my overall available storage space (from 2TB to 4TB total).

However, my problem is trying to determine the best way to go about doing so, with the limited amount of overhead space I have available. In my case, I need to convert the RAID-1 into a RAID-5. But, it won't let me do so until I can delete the data off of the current 2 drives, so that I can create a RAID-5 array from scratch. But, my RAID-5 array will end up with three drives, and I don't have room to push off all of the data off of those two drives onto other random spares elsewhere.

So, my solution that I'm HOPING will work is to copy all of the data off of the RAID-1 setup onto my new 2TB hard drive, and then see if Windows will let me build a RAID-5 setup using just those two drives, then copy the data over from the third 2TB drive onto the RAID-5 setup, and then lastly delete the now duplicate data from the third 2TB drive, and then try to add it into the RAID-5 setup.

Complicated? Yes. Other options? I don't know! I just want to make sure I don't have to re-rip all my movies all over again, so I'm trying to make this as clean and simple as possible. But since it takes ~10 hours every time I copy 2TB worth of data from one drive to another, I don't want to waste my time doing something wrong, that won't work in the end anyway!

Any ideas? Any way I can try to do this with my limited amount of leftover free space?

while it may be possible (link) [n8gray.org]- it certainly isn't advisable, especially without a back-up and involving important data that you don't want to lose (even if you can re-create it)

I agree, you're probably right, it's not a good idea.

I *think* I can squeeze it onto a combination of my other RAID-1 drive that I have other data on, and my backup external HDD, then wipe both drives, then build a new RAID-5 array, and migrate the data back over.

Man, if only I could justify a few hundred dollars to add a hardware RAID card instead!

Never deal with the only copy of your data. Purchase a 2TB external drive, make a copy of your data on it, confirm the data is accessible on the external drive, and then you can freely do anything you want with your raid1->raid5 conversion.

Later on if you don't need that external drive you can sell it or repurpose it for something else.

Hardware raid card is a lot cheaper if you look for used on ebay. I got my LSI SAS9220-8i and the cable for 8 SATA drives for under $70 there and it has good linux and freebsd (freenas) support.

While it may be possible I wouldn't try it on any data I valued. Was reading about someone using ZFS RaidZ and creating the RaidZ pool then degrading it immediately by removing the data drive, copy the data to the degraded array and then restoring the drive, but I wouldn't even begin to risk that.

I ended up squeezing the data into my other drives, and then attempting to build a software RAID-5 array, and then copying the data back over. Unfortunately, Windows is being a bum, and keeps failing when trying to build an empty RAID-5 array. I've verified that all disks are good, but it's still giving me fits. I'll keep messing with it and see what I can do.

But to answer my original question of this thread, I did try to see if Windows would let me build a 2-drive RAID-5 array, and it will not. So, you MUST use at least 3 drives to build the array with.

Quote from ElectroWolf : I ended up squeezing the data into my other drives, and then attempting to build a software RAID-5 array, and then copying the data back over. Unfortunately, Windows is being a bum, and keeps failing when trying to build an empty RAID-5 array. I've verified that all disks are good, but it's still giving me fits. I'll keep messing with it and see what I can do. But to answer my original question of this thread, I did try to see if Windows would let me build a 2-drive RAID-5 array, and it will not. So, you MUST use at least 3 drives to build the array with.

Pretty much. Short of pulling a hack of some sort, i.e., tricking the system that the 3rd disk is there, you need a third drive of some sort. Do you have a third disk laying around (< 2TB presumably) and how tied to windows are you?

Quote from ElectroWolf : Windows is being a bum, and keeps failing when trying to build an empty RAID-5 array.

I would highly recommend you go for the hardware raid instead of the windows raid

Quote from slapshot136 : I would highly recommend you go for the hardware raid instead of the windows raid

That actually depends on the type of server you're running. Unless you're running a high end server that sees a lot of IOPS, Windows might actually be better. The only true benefit to hardware RAID comes with high end cards that have dedicated processors on them. OTOH, Windows' software RAID compares very favorably to medium to low-end "hardware" RAID (which is really offloading to the CPU), and has the benefit of being readable by any Windows installation.

Quote from redmaxx : The only true benefit to hardware RAID comes with high end cards that have dedicated processors on them. OTOH,

you can't even boot off of a windows raid, can you?

Quote from slapshot136 : you can't even boot off of a windows raid, can you?

Yes, yes you can.