How exactly does RAID 1 work (how safe?)

[KevySaysBeNice]

First, here is what I'm thinking about building:

I'll start with a gPC mini-ITX computer from good ol' Walmart. These things are 199, come with a case with plenty of room for a few more hard drives, and use very little power. Then, I'll buy a PCI RAID card, two 750gb SATA drives, I'll plug it all together, install windows XP Pro, and call it a day. The idea would be that this system would be cheap, use very little power, not throw off a lot of heat, and not be too terribly quite.


Anyway, onto the point of this thread, let's say I build this system and start putting photos on it (which is basically the point, to store all of my digital photos). Now obviously RAID 1 will protect me if one of the drives just for some reason dies, but what if there is a bad sector on one of the disks? What if one of the drives slowly starts dieing? I'll admit I don't know a TON about how HDs work, but in the past I've had directories that one day will disapear. Or large sections of a hard drive.

Does RAID 1 somehow check to make sure that both drives are exactly matched, and so if something is missing a red flag will go up?


I guess I'm just wondering how safe RAID 1 is... Assuming I don't have a fire, or any sort of electric storm, or a virus that deletes all of my files, is RAID 1 safe enought count on?

Thanks!

 

[dshankar]

1. The gPC might not be powerful enough in terms of PSU requirements of 2 750GB HDs and a RAID card. It might be cheaper for you to get a cheap motherboard P35 motherboard with RAID 1 built-in and toss two hard drives in there and add a quailty PSU.

2. RAID 1 is very secure. It doesn't do any file checking continuously but it mirrors two copies of every file that you save. File goes to Drive C, copy goes to mirrored hard drive. If you have a bad sector or anything, just copy the other mirrored copy over.

 

[KevySaysBeNice]

Well, let's say one of the hard drives becomes currupt, and a folder of files disappears but I don't notice, because I'm not using the files so I don't notice. Then one day the GOOD drive, that has the non currupt files dies. Then, obviously, I have the still working drive but with missing or currupt files.

I guess I'm just wondering how I go about making sure everything is working.

 

[UICompE02]

It depends on which RAID controller you choose, but many RAID 1, 5, and 6 controllers do what is called a Patrol Read, which performs checks in the background to make sure that the data on both disks match. When a mismatch is found, the RAID firmware or management software should alert you that there is a problem and the array has become degraded.