Can't mirror partitions on Win2k Servers with identical dynamic IDE drives

I have a problem with setup mirroring. Can somebody give me some hints? On a W2k Server with two identical IDE Seagate 15G byte drives setup as dynamic, the 4G byte C partition can be mirrored as expected, but the 10G byte D partition cannot be mirrored. This is what is happening:

The mirroring process starts and then soon stops with an I/O Error message. When I check the D partition for errors, I can find no errors. I changed the second drive to the second controller, but the mirroring error remained.

I unmirrored the C partition and tried to first mirror the D partition, but got the same error. Re-establishing mirroring for the C partition worked fine.

I'm starting to think that data on this D partition could be the source of the trouble. The D partition contains a copy-protected carpenter DOS application. The copy protection is based on a license key string. Somewhere I read that partitions containing temporary Internet files cannot be mirrored. So I will make a separate partition for these potential trouble files and try again. Do you have any other ideas on what I should test?

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It's not likely that a file lock or other data errors would cause mirroring to fail. The Logical Disk Manager sits below the file system. I'm inclined to think that you have a couple of bad sectors on the second drive.

Try this. Create a separate partition on the second drive and format it using the same cluster size as the D partition.

Now run CHKDSK on the both partitions. Compare the total number of clusters. If the second partition has even 1 fewer cluster than the first partition, you cannot mirror them.

This is a fairly common occurrence. I generally leave a little extra space at the end of a drive if I know I'm going to mirror it.

If this is the problem, you can use a tool like Partition Magic to shrink the D partition enough to let you mirror it to the free space on the second drive. You don't need me to remind you to back up your data before you do this.

This was first published in February 2001

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