Category Archives: Products

Articles covering specific products, such as VMware vSphere, vCloud Suite, NSX, vRealize, Horizon Suite.

vRealize Operations 6.7 VM Memory counters

Accuracy of Guest OS memory has been a debate for a long time. I’ve been at VMware for 1 decade and remember the debate between Active RAM and Consumed. Along came the visibility into the Guest OS by vR Ops, which was a major step forward. It is not, however, the final solution yet, as we still have to consider applications.

Take a look at the following utilization diagram:

The first bar is a generic guidance. The 2nd bar is specific to RAM.

  1. When you spend on infrastructure, you want to use it well. After all, you pay for the whole box. So ideally, it’s 100%. The first bar above shows the utilization range (0% – 100%). Green is where you want the utilization to be. Below 50% is blue, symbolizing cold. The company is wasting money if the utilization is below 50%. So below the green zone, there is a wastage zone. On the other hand, higher than 75% opens the risk that performance may be impacted. Hence I put yellow and red threshold. The green zone is actually a narrow band.
  2. In general, applications tend to work on a portion of its Working Set at any given time. The process is not touching all its memory all the time. As a result, the rest becomes cache. This is why it’s fine to have active + cache beyond 95%. If your ESXi is showing 98%, do not panic. Windows and Linux are doing this too. The modern-day OS is doing its job caching all those pages for you. So you want to keep the Free pages low.

Cache is an integral part of memory management, as the more you cache, the lower your chance of hitting a cache miss. This makes sense. RAM is much faster than Disk, so if you have it, why not use it? Remember when Windows XP introduced pre-fetch, and subsequently Windows SuperFetch? If not, here is a good read.

As you can read from the SuperFetch, Memory Management is a complex topic. There are many techniques involved. Unfortunately, this is simplified in the UI. All you see is something like this:

Linux and VMkernel also has its fair share of simplifying this information. This Linux Ate My RAM is pretty famous. For ESXi, a common misperception is “we are short on RAM, but fine on CPU”, when it is actually the other way around! To prove it, check the Max VM CPU Contention and Max VM RAM Contention counter for each cluster.

Windows Memory Counters

  • In Use: this is what Windows needs to operate. Not all of them are actively in used though, which is why the VM Active Memory counter from hypervisor can be lower than this. Notice that Windows compresses its active RAM, even though it has plenty of Free RAM available. This is a different behaviour to ESXi, which do not compress unless it’s running low on Free. Formula is In use = Total – (Modified + Standby + Free)
  • Committed: the currently committed virtual memory, although not all of them are written to the pagefile yet. Commit can go up without In Use going up, as Brandon shares here.
  • Commit Limit: Commit Limit is physical RAM + size of the page file. Since the pagefile is normally configured to map the physical RAM, the Commit Limit tends to be 2x.
  • Modified: page that was modified but no longer used, hence it’s available for other usage. It’s counted as part of Available. The API name is guest.mem.modifiedPages (Win32_PerfRawData_PerfOS_Memory#ModifiedPageListBytes)
  • Standby: Windows has 3 levels of standby. They are:
    • guest.mem.standby.core (Win32_PerfRawData_PerfOS_Memory#StandbyCacheCoreBytes)
    • guest.mem.standby.normal (Win32_PerfRawData_PerfOS_Memory#StandbyCacheNormalPriorityBytes)
    • guest.mem.standby.reserve  (Win32_PerfRawData_PerfOS_Memory#StandbyCacheReserveBytes)
  • Free: guest.mem.free (Win32_PerfRawData_PerfOS_Memory#FreeAndZeroPageListBytes)
  • Cached = Modified + Standby
  • Available = Free + Standby
  • Paged pool: this is a part of Cache Bytes. Based on this great article, it includes Pool Paged Resident Bytes, the System Cache Resident Bytes, the System Code Resident Bytes and the System Driver Resident Bytes.
  • Non-paged pool: this is kernel RAM. It cannot be paged out. It’s part of In Use.

As a result, determining what Windows actually use is difficult. If the UI is not clear, the API is even more challenging. The name in the API does not map to the name in the UI.

Linux Memory Counters

As you can guess from above, Linux does it differently 🙂 There are 5 counters that we’re interested:

  • Total: guest.mem.total (/proc/meminfo#MemTotal)
  • Buffers: guest.mem.buffers (/proc/meminfo#Buffers)
  • guest.mem.cached (/proc/meminfo#Cached)
  • guest.mem.slabReclaim (/proc/meminfo#SReclaimable)
  • Available: guest.mem.available (/proc/meminfo#MemAvailable since Linux 3.14)
  • Free: guest.mem.free (/proc/meminfo#MemFree)
Used = total - free - buffers - cache 
Cache = guest.mem.cached + guest.mem.slabReclaim

The above mapping and calculation are based on latest Linux document and source code. As older Linux has used different formula, the future may change.

vR Ops Counters

How are the above Guest OS metrics appears in vR Ops? VMware vSphere Tools comes to the rescue! It provides a set of counters (details here). The counter Memory Needed considers Standby Cache Normal Priority as part of needed memory. As you can see in this example, that is a whopping 40% of 10 GB RAM. Notice the Free and Zero is left with just 1 MB. Windows does not include this, hence Windows reports a lower number than vR Ops.

vR Ops can’t change the value as that value is coming from Tools. We do not have the metric for Cache. We are working closely as a team to provide more details mapping to Guest OS. In the meantime, you can use Endpoint Operations module of vR Ops. Do note that this requires agent deployment, so keep it only for your critical VMs.

The changes in vR Ops 6.7 is the mapping of VM counters. We did not come up with a new counter. All the counters were already available since vR Ops 6.3, and I explained the counters in this post. In 6.7, the Memory Workload counter and Memory Usage now map to Guest OS instead of Active. If the Guest OS is not available, it falls back to Consumed. This is why you start seeing a jump in memory usage. It’s not that vR Ops 6.7 chooses the wrong counter. It’s merely using a different counter.

vR Ops 6.6 uses VM Active
vR Ops 6.7 uses Guest OS, then VM Consumed

If you want to come back to Active, which I’d not recommend, here are the counters you need:

For Alerts, you can simply change the metrics used in the symptom. For Dashboards, you can create a custom dashboard that use these metrics instead.

What counters to use?

It depends on the context. Are you troubleshooting performance or analysing for right sizing? Performance is about “Does the application get what it needs?“. What the long term or big picture is less relevant. Right sizing is about “Overall, what is the right amount needed”. You look at long term. A 5-minute burst should not dictate your overall sizing recommendation.

  • For Performance:
    • VM Memory Contention. No point increasing/shrinking the Guest if the problem is with the hypervisor.
    • Guest OS Page-In Rate. A heavy page-in impacts performance. Page-In is not an metric for capacity due to pre-fetch.
    • Guest OS Memory Needed.
  • For Capacity:
    • For best performance: Guest OS Memory Needed
    • For lowest cost: Guest OS Used (need agent), Guest OS Cache (need agent)

I hope the article helps to clarify. What counter do you want to use in future version of vR Ops? Discuss with your TAM or SE, as they will champion you internally in VMware. If you do not have one, let me know at e1@vmware.com.

Monitoring PostgreSQL Server

This blog is contributed by my friend Luciano Gomes, a VMware Technical Account Manager in Rio de Janeiro Area, Brazil. Thank you, Lucky!

vRealize Operations can monitor many databases in the market, including PostgreSQL. If you have the Enterprise license for vR Ops, the Plugin for PostgreSQL is for free. If you would like to monitor Oracle Database or MySQL, please visit BlueMedora for more information.

Pre-requisites:

  1. vR Ops Enterprise Edition
  2. Endpoint Operations Agent
  3. PostgreSQL plugin
  4. PostgreSQL adjustments

Steps:

  1. Download the PostgreSQL plugin, from VMware Marketplace here
  2. Follow the instructions to install this Plugin here
  3. Download the EP Ops agent (must be the same of your vR Ops version) here
  4. Install the EP Ops agent, instructions here
  5. Adjust your PostgreSQL:
    • Edit the file pg_hba.conf and change the line:
      • from: local all all peer to: local all all md5
      • and add something like that: host all all localhost md5
      • Your postgres user, need to have a password: 
        • sudo -u postgres psql postgres \password postgres
      • Ensure that the user has the permission to view tables and statistics objects in the PostgreSQL cluster. For example:
        • GRANT SELECT ON ALL TABLES IN SCHEMA public TO <username>;
  6. Configure PostgreSQL credentials in vR Ops:
    • In the left pane of vRealize Operations
      • Click Administration, then click Inventory Explorer.
      • Select Adapter Instances > EP Ops Adapter Instance.
      • Select the PostgreSQL instance for which you want to collect metrics and click the Edit Object icon. The Edit Object dialog box opens.
      • Click on the Add New plus sign beside Credentials. You will see the Manage Credentials dialog box.
    • Enter the credential details.
      • Credential Name
      • postgresql.user
      • postgresql.pass
  7. Import the Dashboards from here and happy customizing!

Hope you like it!

Monitoring Data Center Power Consumption

This blog is contributed by my friend Luciano Gomes, a VMware Technical Account Manager in Rio de Janeiro Area, Brazil. Thank you, Lucky!

This dashboard helps you measure, understand and predict the power consumption of your Datacenter. vRealize Operations also allows you to measure how much power a particular Virtual Machine is consuming and how much that Virtual Machine will consume in the future. 

You need vR Ops Advanced Edition as the minimum, as custom dashboard is required.

Step 1: enable Power Metrics metric

Choose your active policy, and follow as shown below:

Step 2: Import the dashboard and view

I’ve prepared them here

Voila! That’s it!

Hope you find useful. If you have other requirements for vR Ops dashboards, let me know!