I have about 20K of music files and photos.  For some reason when I run a library scan on Windows Media Center 7 it takes a long time.  The progress bar seems to process a few files every few minutes.  What I find strange is that when I check/refresh the device status page, I notice that for every read on the disk there is a write to the parity drive.  Is this normal?  Has anyone experienced this with WMC?  If WMC is just reading the library why would there be parity writes?

I have about 20K of music files and photos.  For some reason when I run a library scan on Windows Media Center 7 it takes a long time.  The progress bar seems to process a few files every few minutes.  What I find strange is that when I check/refresh the device status page, I notice that for every read on the disk there is a write to the parity drive.  Is this normal?  Has anyone experienced this with WMC?  If WMC is just reading the library why would there be parity writes?

because it is writing?

You're making the assumption that the library scan only reads the files.  It's entirely possible that WMC is writing metadata, or something similar during the scan. 

Windows 7 does cache some info on the Library scan, but I have never seen it save any info out on the share.  It should all be under C:\Users\<username>\AppData\Local\Microsoft\Media Player

Yes, I made the assumption it wouldn't write for the reason StevenD pointed out.  Was just wondering if anyone else had a similar experience.

You can try running lsof | grep /mnt/user at the command line to see what's being accessed during the scan.