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RAID1 vs Windows dynamic disk mirror - does it do error correction?

Posted on 2014-10-26
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Last Modified: 2014-11-09
One of the benefits of a RAID1 array is that the array can detect and automatically correct errors that occur in individual disks at the sector level. When one disk develops a bad sector, the sector is remapped and the good data is copied from the other disk. Even if the sector is not explicitly bad, inconsistencies in the data that was written can be detected and corrected. ZFS does this by "resilvering", other RAID cards like LSI or Adaptec do it by "patrol read" and "consistency checking".

This helps you avoid small amounts of corruption - a byte here, a byte there - from growing on your disk over time.

Do you get these same benefits when using Microsoft Windows 7's Dynamic Disks feature to create a two disk mirror in Disk Management?
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Question by:Frosty555
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dbrunton earned 250 total points
ID: 40405233
Perhaps not.

Mirrored Volumes

A mirrored volume is a fault-tolerant volume that provides a copy of a volume on another disk. Mirrored volumes provide data redundancy by duplicating the information contained on the volume. The two disks that make up a mirrored volume are known as mirrors. Each mirror is always located on a different disk. If one of the disks fails, the data on the failed disk becomes unavailable, but the system continues to operate by using the unaffected disk.

Mirrored volumes are available only on computers running the Windows 2000 Server family or Windows Server 2003.

from http://technet.microsoft.com/en-us/library/cc737048%28v=ws.10%29.aspx

That to me says it is not working at sector level but at disk level for redundancy.

Could be wrong.  Wait for some other experts to comment.
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by:noxcho
noxcho earned 250 total points
ID: 40405259
The answer is no. The hardware RAID is built on sector level and it can have such feature. In dynamic drives mirror you mirror the file systems which are the overlayer of sectors. Dynamic mirror mirrors only data for redundancy purpose.
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by:andyalder
ID: 40411429
I think the answer is yes: "When a read from one plex fails, the bad sector is recorded. DMIO then reads from the other plex and writes back to the first plex." http://support.microsoft.com/kb/325615

It doesn't do a background scan as far as I know though, and I'm not even sure chkdsk scans both plexes for bad sectors.
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