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What do the return values of my Xen sensors mean?

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When I monitor a Citrix XenServer, for example, with PRTG’s Xen server host sensor, the return values in channels like network send and receive seem to be very odd. Could you please clarify what these numbers mean?

citrix prtg sensor values xen xenserver

Created on Feb 8, 2013 10:13:44 AM by  Gerald Schoch [Paessler Support]

Last change on Feb 8, 2013 10:49:31 AM by  Daniel Zobel [Paessler Support]



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This article applies to PRTG Network Monitor 12 or later

How to Understand the Values of Citrix XenServer Sensors

PRTG displays values for traffic as these are extracted from Xen devices. For example, the Citrix XenServer Host Sensor can show network traffic for an interface IF. The data is extracted from the variable pif_IF_rx (bytes per second received on physical interface IF) and pif_IF_tx (bytes per second sent on physical interface IF).

Unfortunately, you cannot use this data to generate reports in PRTG. It is only possible to get snapshots in time; there are not any counters. These values cannot be processed in reports.

However, you can review the data manually:

  • Xen API stores persistent performance data in round robin databases (RRDs) using a fixed structure.
  • You can review the raw data read by PRTG with your browser via /rrd_updates: https://<host>/rrd_updates?start=<timestamp>&host=true
    • Replace the placeholder <host> in the address with your Xen server’s IP or FQDN.
    • The parameter start needs to be provided using Unix-type timestamp; replace the placeholder <timestamp>. We recommend using the timestamp “five minutes ago” (see Epoch & Unix Timestamp Conversion Tools). Then you will receive report data for the last five minutes.
    • The query parameter host=true enables to obtain not only VM data, but host data as well.
    • You will have to enter your Xen server credentials to access this data.
  • This will provide data for the queried host in an XML format with RRDtool ‘xport’ style. Because this format is hardly readable, you can use a tool to view the results in a table (for example, DSreport).
  • To find the values of your interest, look for the specific counter. For example, if you want to know the received traffic on the interface eth0 of your Xen server, look for the entry pif_eth0_rx.
  • You can find an overview of counter definitions on Xen Wiki.

Here is an overview about the RRD values PRTG uses (CAPS in values are placeholders):

ValueChannel
cpuNCPU N Usage
loadavgLoad Average
pif_IF_rx /vif_IF_rxNetwork IF received
pif_IF_tx/vif_IF_txNetwork IF sent
pif_IF_rx_errors/vif_IF_rx_errorsNetwork IF errors received
pif_IF_tx_errors/vif_IF_tx_errorsNetwork IF errors sent
sr_SR_cache_sizeIntelliCache size SR
sr_SR_cache_hitsIntelliCache hits on SR
sr_SR_cache_missesIntelliCache misses on SR
vbd_DEV_writeWrites to DEV
vbd_DEV_readReads from DEV
vbd_DEV_write_latencyLatency write DEV
vbd_DEV_read_latencyLatency read DEV
memoryMemory available
memory_targetVM balloon driver target
memory_internal_freeMemory used
memory_total_kibTotal Memory used
memory_free_kibTotal Memory free
xapi_memory_usage_kibTotal Memory XAPI
xapi_free_memory_kibMemory free XAPI daemon
xapi_live_memory_kibMemory live XAPI daemon
xapi_allocation_kibMemory allocation XAPI daemon
runstate_entry_timeRunstates exist
runstate_fullrunAll VCPUs running
runstate_full_contentionAll VCPUs runnable
runstate_concurrency_hazardVCPUs running or runnable
runstate_blockedVCPUs blocked or offline
runstate_partial_runVCPUs running or blocked
runstate_partial_contentionVCPUs runnable or blocked

Created on Feb 8, 2013 10:41:54 AM by  Gerald Schoch [Paessler Support]

Last change on Feb 8, 2013 10:43:46 AM by  Gerald Schoch [Paessler Support]



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Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.