How are Vscan requests balanced between multiple Vscan servers?

Applies to

Answer

• Vscan Request Distribution:
  • No specific algorithm (e.g., round-robin, least busy) is used to distribute Vscan requests.
  • Each ONTAP AV Connector in a scanner-pool opens a named pipe to the SVM to listen for pending Vscan requests.
• Named Pipe Operation:
  • ONTAP places data into the named pipe, which operates on a first-in, first-out (FIFO) basis.
  • The pipe functions like a message queue, preventing multiple servers from processing the same request.
  • All AV Connectors place a READ call on the pipe, allowing them to see any new scan request written by the SVM.
• Vscan Server Responsibilities:
  • Each Vscan server (via its AV Connector) is responsible for reading and processing requests from the pipe in a timely manner.
  • When the SVM writes a scan request to the pipe, all AV Connectors are notified and attempt to read it.
• Request Processing:
  • The first AV Connector to respond to a scan request removes it from the pipe, signaling to other AV Connectors that the request is being handled.
  • This ensures only one AV Connector processes the request, preventing duplicate processing.
• Acknowledgment and Communication:
  • The responding AV Connector sends an ACK to the SVM, informing it which AV Connector is handling the scan request.
  • ONTAP and the AV Connector do not decide which server processes a request; the first AV Connector to respond and acknowledge determines responsibility.

Additional Information