Mirroring vs Raid

My Windows 7 is currently installed on a raid 1 array. I am considering on switching from hardware raid to windows 7's mirroring function as hardware raid tends to be problematic if the motherboard dies or is replaced. I am however curious on a number of issues.

First of all, is this a good idea at all. Will I suffer a very serious performance loss? Minor losses aren't that big of a deal but I don't want to regret this. Is windows 7 mirroring a "true" mirroring?

Are both disks bootable? Consider the main disk dying. In RAID 1 I can simply boot without doing anything (aside from pulling out the dead drive). If my main drive dies will the mirror be bootable?

How good is it in terms of avoiding data corruption or loss?

Does windows 7 mirroring provide a performance gain (during read)? It could be twice as fast as there are two disks to read from...

I am planning on making this switch without reinstalling windows. I basically plan on pulling one of the raid disks off the array, format it. Boot from the other disk in raid... Use windows 7 mirroring to make a carbon copy. Remove the remaining disk in raid. Boot from the mirror. And finally use windows mirroring function on the original raid'ed drive.

I agree, with a couple caveats.

Does windows 7 mirroring provide a performance gain (during read)? It could be twice as fast as there are two disks to read from...

Depends on the system, but generally, yes, there is a little gain, but it is not twice as fast. The seek times are not increased, only the actual reads. There might be a very slight hit in writes - however, but that is not normally something folks see.

Both disks will be bootable, but ONLY IF the reason to break the RAID and boot from one or the other is due to disk failure. In a RAID, if corruption is due to malware or something other than physical failure of a single disk, then neither disk may boot as the corrupted or infected file would be mirrored on both drives. So there is still a need for current backups.

Motherboard's do not have hardware RAID, they use the CPU - if you want real RAID buy a proper ($$$) card. As for data loss, store one backup offsite and the other somewhere else, such as a NAS box.

So basically using this I can migrate my windows installation from a hardware raid (real or not :P) to a software raid (windows 7 mirroring) without problems. Right?

Frostmourne said:

Motherboard's do not have hardware RAID

WHOA! WHOA! WHOA!!!! That is way incorrect. MANY MANY motherboards have integrated RAID controllers on board! And have for years! You are correct when you say they use the CPU, but an on-board RAID controller is still a hardware RAID. Your statement would be the same as saying on-board graphics, on-board sound, or on-board LAN are not hardware! They most certainly are hardware. But just like a graphics card vs. on-board graphics, a RAID controller "card" is much more capable than an on-board controller, not just because they tend to have more capable components, but because they relieve many of the duties from, and free up other motherboard resources (namely the CPU, RAM, and bus).

So now that we have established that many motherboards do indeed have on-board hardware-based RAID controllers, let's look at the differences here.

First, there are software based RAID systems that basically take two drives (or two partitions on one drive) on standard IDE or SATA interfaces (not RAID interfaces) and treat them as 1 RAID device via a software "program" running in the background. This topic is not about them, and I would not recommend a software based RAID to anyone.

Then there are on-board controllers as found on most new motherboards today. These are hardware devices, however, they typically offer fewer RAID options, and they do use more system resources. But, they are still very effective and capable devices, more than suitable for most users, even hard-core enthusiasts (though they probably would never admit it!).

Then there are add-on cards. These also use some system resources (drivers have to be installed, just like any other hardware device) and the OS must be configured to use it. But RAID controllers cards, just like graphics cards, tend to include a separate more powerful and dedicated processor, dedicated memory, controllers and other associated components, and the necessary drive connections. These are primarily for file servers or where a robust redundancy is "mission critical". Cards are also essential for hard-core gamers with deep pockets seeking bragging rights (and nothing wrong with that).

The biggest advantage to cards over on-board RAID, IMO, is portability. With on-board RAID, if the motherboard fails for any reason, you lost your RAID. But with a card, you can move the card and connected RAID "array" to a different computer and be on your way.

I'm not a big proponent for using RAID 1 (mirrors) at home.

The use of RAID1 here just allows your OS to keep running in the event of a hard drive failure.

I disagree. While I do agree everyone should have a viable backup plan, the use of RAID1 at home makes perfect sense in the event a hard drive fails. Without RAID1, a drive failure means total data loss and for many, the data is MUCH more valuable than the OS and hardware. Without RAID1, the only chance of recovery from a drive failure is a backup - which most people don't use, or don't keep very current.

With a home machine, I think it's far less problematic if you have to take the machine down for awhile while you reinstall your OS or restore an image that you made and then put your data back.

Oh? Have you ever had a drive fail in RAID1 array? I have and simply pulling the bad and inserting a new drive and letting the controller do the rest (while you keep on computing barely losing a stroke) is FAR LESS problematic than pulling the old drive, inserting the new, resinstalling Windows, drivers, all your security programs, all the updates, and then restoring your data from the most recent backup. It is definitely less problematic than restoring from an image file - which is not likely to be current.

And as for backups - a RAID1 provides a very easy method of having a fairly current backup. Just swap in the spare drive every week, and put the removed (now the spare) drive in a safe place - like a bank safety deposit box. Then next week, swap them again, they sync and become current and you are good to go.

Frostmourne said:

With on-board RAID, if the motherboard fails for any reason, you lost your RAID. But with a card, you can move the card and connected RAID "array" to a different computer and be on your way.

I have used motherboards with Intel IHCxR controllers and was able, very easily, to move to another board with the same or later Intel controller with no data loss. Obviously the operating system needed to be repaired/reinstalled if new board was different but RAID was recognized and all data was intact.

Moved from ASUS P4P800 E Deluxe (ICH5R) to Gigabyte GA P45 UD3P (ICH10R).