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We run a HyperV server on RAID-6 (the OS is Windows Server 2008 R2). The hardware is LSI MegaRaid SAS 8704EM2 controller, with 4x 1TB WesternDigital SATA drives. The server is up & running on this hardware for 4 months already.

Every week however, there's a warning message in the MegaRAID storage manager dashboard saying, I quote, "Patrol Read can't be started, as PDs are either not ONLINE, or are in a VD with an active process, or are in an excluded VD". Don't ask me what's PD or VD - I don't know.

I've googled and discovered the following:

  • Patrol read (also available on Intel and Dell RAIDs) is useful diagnostic procedure that checks that all data on all drives can be read.
  • The official documentation "Appendix A Events and Messages" only lists the possible messages (without any hints on fixing the conditions). It also says "Warning" error levels means "Some component may be close to a failure point".

Should I worry about my data? How do I fix the thing?

Thanks in advance!

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PD: Physical Disk (the drive that's plugged in), VD: Virtual Disk (the disk that the OS sees). – DerfK Apr 15 '11 at 15:49

When you open the Dashboard does it say the RAID is doing some Background Operations (Virtual drive operations in progress or Drive operations in progress) or Does the log say operations like Consistency Check started some time before the warning about the Patrol Read and some time after that it (Consistency Check) finished?

Only my guess but: Check your Consistency Check settings (right click on the controller name > Schedule Consistency Check) if it is run continuously (non-stop) or if it runs some time before Patrol Read and it cant finish on time for the Patrol Read to start You can also try to set Patrol Read settings in the raid controller (right click on the controller name > Set Patrol Read Properties) to start/run a day after the consistency check

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Angel is right! Patrol Read (PR) will be cast out of the command cue if any background operation and CC is started. PR will not restart again until you manually start it or it starts at a scheduled time. The best thing for you to do is to schedule the PR ahead of the start of a CC so it has enough time to complete. – user141670 Oct 18 '12 at 14:58

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