A few RAID 1 questions

[JMJ]

Hi, have a few RAID 1 questions if someone can answer them:

1. Is it possible to have a corrupt file on 1 drive and not the other? Has anyone ever seen this?

2. Is it possible to swap the SATA connections (now running off the mirrored drive) and copy all contents of the mirrored drive onto what used to be the primary drive? I have never heard of nor seen an option like this, I set the RAID 1 up when I built the system. I thought at one point I had seen something about RAID in windows, but now I can no longer find it. It may have been on an older system, I just can't remember.

Thanks

 

[drizzt81]

1. Is it possible to have a corrupt file on 1 drive and not the other? Has anyone ever seen this?

Yes, it is possible. Most RAID-1 implementations do not compare file data during reads. If the HDD does not notice data corruption in one or more sectors of a file, it is possible that the two HDDs have different data. Note that most HDDs have some form of error detection and possibly correction mechanism. The data corruption would have to be so severe or targeted to 'fall through the cracks' without being noticed. My lack of experience prevents me from putting a number of the likelihood of this event. However, my gut feeling tells me that it is rather unlikely.

 

[uOpt]

Even if raid-1 would compare both disk's data on read (and thereby lose the performance benefit of raid-1), then in a two-disk raid-1 it wouldn't know which data is right.

It certainly can happen if the disk itself corrupts data or if the cable is very wonky (base error checking is done on the cable's communications). Bad raid software (such as most likely in onboard sata raid) certainly can cause it, too.

The best way to prevent this would be to look at SMART's ECC recovered numbers often.

 

[Ockie]

Hi, have a few RAID 1 questions if someone can answer them:

1. Is it possible to have a corrupt file on 1 drive and not the other? Has anyone ever seen this?

It's very possible, it happened to me. You can also have one drive acting funky too due to defects.

2. Is it possible to swap the SATA connections (now running off the mirrored drive) and copy all contents of the mirrored drive onto what used to be the primary drive? I have never heard of nor seen an option like this, I set the RAID 1 up when I built the system. I thought at one point I had seen something about RAID in windows, but now I can no longer find it. It may have been on an older system, I just can't remember.

Thanks

I don't get your last question, are you asking that if you were to take a RAID1 mirrored drive pair, pull a drive out, and swap it with some other system drive, will it format that drive and mirror the existing data onto that swapped drive? If thats the question then yes.

When you insert a clean or replacement drive into the RAID1 system, it will format and prep the drive prior to mirroring the files over, so you could really put anything on there, it would just clear it out.

If you are talking about just swapping around the two mirrored drives by moving the sata connections, it should still function.