RAID5, NTFS and Dynamic Disk Problem

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reanimationxp

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Nov 14, 2007
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Hey all,

I have (or had) a 3x750GB RAID5 array set up on an nForce 780i motherboard, using nVidia's RAID5. Upon setting up the array I thought it was hardware RAID, and was thus surprised when the performance sucked, but that's quite a while ago.

I recently bought a 4th 750GB drive, hoping to extend my existing 1.3TB RAID5 volume by an additional 750GB, bringing my total usable space to just over 2TB (with a drive's worth of space being used by parity). nVidia's control panel would not let me add the newly found drive to the existing array, so I figured array extending was something that was not supported on the drivers. Pain in the ass, but no big deal.

I backed up my ~1.2 Terabytes of data, and erased the array. Using the in-bios RAID utility, I created the new array and added all 4 of my drives to it successfully. However, when I went back into Windows XP, I see a partitionable space of only 54GB. From within Windows, I decided to use the nVidia utility to erase the array and try again. After erasing, I went to add all 4 disks to a new RAID5 array, and discovered that the nVidia utility would only allow me to add 3 of them, and the "Next >" option was greyed out if I tried to add the 4th. After doing some research, I've discovered that the maximum volume size for a basic disk in Windows XP is 2TB, and I believe this is why the utility is not allowing me to add my 4th disk.

I then looked into ways to breach this 2TB limit, and Dynamic Disks was one of the options. Since I don't have "real" hardware RAID5 anyway, this is an option I would consider, but I have a couple concerns. I upgrade systems fairly frequently, and have heard horror stories of trying to move Dynamic disks, particularly in arrays, to new machines. I figured any motherboard with an nVidia chipset would happily accept my nForce RAID5 array, which is why I chose to use it rather than dynamic disks to begin with.

Can anyone tell me how easy it is to transfer dynamic disk arrays between windows installations, in the case that the first install should crash? What are the disadvantages of using dynamic disks? If I fronted the money for a nice hardware RAID5 solution, would I be able to breach this 2TB limit? I don't have a problem busting partitions into <2TB sizes, but would like to have it all in one array. Right now it appears my best option is to go back to using 3 disks in RAID5, and use my new 750gb as a simple sata, which sucks. I want redundancy should I have a physical drive failure AND ALSO be able to move my array to a new box should Windows crash.

Halp!
 
Welcome to the world of shitty software NVRAID.

To get past the 2TB limit, you'd have to use GPT (GUID Partition Tables) in order to address >2TB arrays; not all Windows versions support this, IIRC, Windows XP x86 does not, but VIsta Ultimate and Windows Server 2008 does.

Dynamic disks in my experience has just never really been a good solution; they're non-expandable and quite proprietary, though I don't see why you wouldn't be able to migrate disks between different Windows systems, especially if the data for the RAID set is on the metadata on the drives themselves.

Even if you used a hardware RAID card, you wouldn't be able to address more than 2TB per array if you still used MBR (Master Boot Record) partition styles for one large partition, on a Windows environment, you must use GPT.

Seems like you've gone through an awful lot of trouble because of crappy NVRAID and Windows Dynamic Disks, you might just be better served to suck it up and get yourself a quality hardware RAID card, or look towards other redundant storage solutions, such as unRAID or WHS.
 
Thanks for the reply. Whether or not the metadata is stored on the drives themselves is exactly what I'm wondering, more or less. With the NVRAID system, I know for a fact that the system, if set up for RAID on those particular ports, will piece together the array on an entirely new motherboard. With dynamic disks, I'm not so sure.
 
I found this article on large logical unit support in Windows, and you are correct that GPT style partition tables don't seem to be supported on Win x86. I did however catch this:

"Note: Disk devices with more than 2 TB of disk space must be converted to GPT format for all of the disk space to be usable. If the device uses MBR format, the disk space beyond 2 TB will be unusable."

My questions now are, if it's possible to create a dynamic disk RAID 5 array in Win x86, what exactly is it not compatible with? That would hint that it IS compatible with GPT tables, just not ones larger than 2TB. Secondly, because of the quote above, would I be able to get away with using all my space in Win x86 somehow on a single volume using dynamic disks if I simply don't allocate the space beyond 2TB? Could I somehow do the same with NVRAID? I'd be willing to sacrifice the last 50GB or so if I could sort of achieve my goal here.
 
I wouldn't count on dynamic disks being portable between systems.
Even changing the drive order on my old Gigabyte motherboard (changed some
of the BIOS settings for the storage devices) rendered some of the dynamic disks broken.

Although you're supposed to be able to import foreign disks
from outside systems, it doesn't work reliably.

Bottom line, dynamic disks are, in my opinion, an unnecessary extra risk and just more
metadata that can get messed up. Stick w/ basic disks for windows, or get a raid card.
 
Thanks alamone, that kind of experience is something I had heard of and someone experienced with it is exactly what I was looking for. Based on that, I'll happily avoid them :) I am intrigued by the unRAID and WHS solutions. I was wanting to avoid running an entire box with the RAID array on it, because as of right now my special folders (Desktop, My Documents) actually reside on my RAID5 on drive D. This is basically to provide some redundancy should a drive fail, without the need to backup, as well as conserving space rather than a mirror-type setup. Because I'm using it that way at the moment, a separate box running an environment specifically for NAS purposes isn't really what I'm looking for, but I may need to switch to a standard backup solution if I want to use my drives as I'm describing.

I have some thinking to do it seems.. :)
 
reanimationxp said:
Thanks alamone, that kind of experience is something I had heard of and someone experienced with it is exactly what I was looking for. Based on that, I'll happily avoid them :) I am intrigued by the unRAID and WHS solutions. I was wanting to avoid running an entire box with the RAID array on it, because as of right now my special folders (Desktop, My Documents) actually reside on my RAID5 on drive D. This is basically to provide some redundancy should a drive fail, without the need to backup, as well as conserving space rather than a mirror-type setup. Because I'm using it that way at the moment, a separate box running an environment specifically for NAS purposes isn't really what I'm looking for, but I may need to switch to a standard backup solution if I want to use my drives as I'm describing.

I have some thinking to do it seems.. :)
Click to expand...
It's a common misconception that RAID offers any sort of "backup", sure it will give you protection against physical disk failure and the like, but any sort of RAID corruption or any accidental deletion won't be under the protection of RAID, which is intended for uptime, not backup.

Just remember that. ;)
 
trust me i've had my fair share of raid problems, which is why i'm as versed as i am already.. i always keep that in mind :) unfortunately the amount of stuff i would back up virtually equals the majority of the drive space i have. taking the cheap way out currently to avoid at least one type of catastrophe.
 
I recently stumbled upon a true "software" RAID solution called FlexRAID, created by one of the members of this forum. I was wondering if anyone has used this, if it's reliable, and if there are any other packages around that offer a sort of driverless RAID solution. Much like dynamic disks, but without the worry of a Windows crash.
 
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