vCenter Performance Tab – Real-time vs. Historical Data

Recently I received a question about the Performance tab within vCenter which intrested me. Looking at the available Chart Options we can see that there are two distinctive performance streams:

  • Real-time data
  • Historical data

Real-time Data
 The Real-time data is displayed for the last hour only and is directly queried from the ESX Host (vpxa) every 20 seconds.
Because the ESX Host stores the performance data locally for the last hour you can have a vCenter outage for up to one hour without getting any gaps in the historical data.

Historical Data
The process outlined below described the steps that are taking place to collect and store the Historical Data.

  1. Every 5 minutes 1/6th of the total amount of ESX Hosts (vpxa) is queried for performance data;
  2. The vpxa sends its data to vCenter (vpxd) which stores the data in the VPX_HIST_STAT1 table.

This process happens every 5 minutes which means that every ESX Host is queried once every 30 minutes.

Let’s take a look at a 10 ESX Host cluster for example:

10.00am: ESX01, ESX02 are queried
10.05am: ESX03, ESX04 are queried
10.10am: ESX05, ESX06 are queried
10.15am: ESX07, ESX08 are queried
10.20am: ESX09, ESX10 are queried
10.25am: ESX11, ESX12 are queried
10.30am: ESX01, ESX02 are queried again.

Every 30 minutes the final statistics data rollup and purge store procedures will run. These database roll-up jobs are either controlled by the SQL Agent (in both MS SQL and Oracle) or by vCenter (vpxd) internally. The vpxd internal scheduler is only used with Microsoft SQL Express Editions.

The corresponding database tables that are used to store the rollup data are outlined below:

VPX_HIST_STAT1 stores integral values at the lowest level of granularity (daily level)
VPX_HIST_STAT2 Weekly Stats Rollup Job – repeats every 30 minutes – performing rollups at weekly level.
VPX_HIST_STAT3 Monthly Stats Rollup Job – repeats once per 2 hours – performing rollups at monthly level
VPX_HIST_STAT4 Yearly Stats Rollup Job – repeats twice a day – performing rollups at yearly level


The interval duration for the stored data is a configurable item from within vCenter as you can see in the screenshot below.

Please note that changing the Interval durations can have a major impact on the database size and vCenter performance due to excessive load.

To conclude, knowing the difference between the Real-time and Historical Data querying and the way the data is processed might benefit you during troubleshooting.

Leave a comment


  1. Nick

     /  March 2, 2011

    Hi vKen.
    Since you’re working with Virtual Connect and ESX(i?), have you encountered the same problem that I currently have?
    Running ESXi 4.1 on BL460G6, with Flex-10, if I load the performance charts to look at the network of a host, I don’t see Any statistics; every column, for every vmnic is 0. The guest’s are running and vmotion etc works, but none of the traffic shows up. It’s a bit of a mystery to me, and I wondered if you had already conquered this issue?

  2. Hi Nick,

    I’m not onsite anymore at the Flex-10 project. I’m wondering however if this is a specific problem to Flex-10 in combination with ESXi 4.1 / vCenter.
    I will send the guys at the site an e-mail to ask if they are experiencing the same things.


  3. Nick

     /  March 7, 2011

    Hi Kenneth,
    I really appreciate you taking the time to answer; I haven’t managed to get any response out of the HP or vmware forums with the same question. If your contacts answer, it would be great to know.

  4. Hi Nick,

    I’ve verified it on the “other” environment and same issues apply, all vmnic’s display 0.
    ESX 4.1.0 – 260247


  5. Nick

     /  March 20, 2011

    Hi Kenneth,
    Thanks for following that up. At least it’s not just me!

  6. Marcel_P4500

     /  March 21, 2011


    Same apllies in my environment, P4500 SAN + c3000 + vcenter + vsphere esxi 4.1 260247 – all 8 flex-nics show 0 …

  7. TheJimmy

     /  August 23, 2011

    What happens if the interval is custom? How do you determine what interval/stat table is being used? Thanks.

  8. Emiliano De Simoni

     /  October 21, 2011

    Try to update the HP Broadcom Nextreme II driver.
    You can do grab from here:

    It seems that bundled driver doesn’t work with statistics.
    That solved the issue for me.

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