Yellow Bricks

by Duncan Epping

esxi

Where to find the Host Client vSAN section?

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I had a couple of people asking already, so I figured I would do a short post on where to find the ESXi Host Client vSAN section. It is fairly straight forward, if you know where to click. Open the Host Client by going to https://<ip address of your host>/ui. Next do the following:

  • Click on “Storage”
  • In the right pane, click on “vSAN Datastore”
  • In the left pane, click on “Monitor”

You should now see the following:

I drew a red rectangle around the vSAN specific menu options. Just click through them. Just for demonstration purposes I disabled the VMkernel interface for vSAN on this host. As you can see in the “Hosts” section below this particular host has no “IP” address indicating you should check the network… Very useful for sure when troubleshooting.

Of, of course the Health Check and the new Config Assist option vCenter also calls this out! With a link to the object even to fix the issue. If you would click the blue link you would go to the VMkernel config section in the UI… I love it how easy it becomes to fix and detect issues. Great work vSAN team!

Getting a 404 error with the Host Client

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Just a short post. I was getting a 404 error with the Host Client when hitting https://<ip of esxi host>/ui. No clue what it was caused by. I re-installed the latest version of the host client but that didn’t solve it. Then I noticed that my endpoints.conf had “/ local” missing. You can check that as follows when logged in through SSH:

cat /etc/vmware/rhttpproxy/endpoints.conf

I did the following (edit + restarted the HTTP reverse proxy) to get it working again:

Edit the config file:

vi /etc/vmware/rhttpproxy/endpoints.conf

add the following:

/ local 8309 redirect allow

Restart the service:

/etc/init.d/rhttpproxy restart

I have memory pages swapped, can vSphere unswap them?

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“I have memory pages swapped out to disk, can vSphere swap them back in to memory again” is one of those questions that comes up occasionally. A while back I asked the engineering team why we don’t “swap in” pages when memory contention is lifted. There was no real good answer for it other than it was difficult to predict from a behavioural point of view. So I asked what about doing it manually? Unfortunately the answer was: well we will look in to it but it has no real priority it this point.

I was very surprised to receive an email this week from one of our support engineers, Valentin Bondzio, that you can actually do this in vSphere 6.0. Although not widely exposed, the feature is actually in there and typically (as it stands today) is used by VMware support when requested by a customer. Valentin was kind enough to provide me with this excellent write-up. Before you read it, do note that this feature was intended for VMware Support. While it is internally supported, you’d be using it at your own risk, and consider this write-up to be purely for educational purposes. Support for this feature, and exposure through the UI, may or may not change in the future.

By Valentin Bondzio

Did you ever receive an alarm due to a hanging or simply underperforming application or VM? If yes, was it ever due to prolonged hypervisor swap wait? That might be somewhat expected in an acute overcommit or limited VM / RP scenario but very often the actual contention happened days, weeks or even month ago. In those scenarios, you were just unlucky enough that the guest or application decided to touch a lot of the memory that happened to be swapped out around the same time. Which until this exact time you either didn’t notice or if you did, didn’t pose any visible threat. It just happened to be idle data that resided on disk instead of in memory.

The notable distinction being that it is on disk with every expectation of it being in memory, meaning a (hard) page fault will suspend the execution of the VM until that very page is read from disk and back in memory. If that happens to be a fairly large and contiguous range, even with gracious pre-fetching from the ESXi, you’ll might experience some sort of service unavailability.

How to prevent this from happening in scenarios where you actually have ample free memory and the cause of contention is long resolved? Up until today that answer would be to power cycle your VM or using vMotion with local swap store to asynchronously page in the swapped out data. For everyone that is running on ESXi 6.0 that answer just got a lot simpler.

Introducing unswap

As the name implies, it will page in memory that has been swapped out by the hypervisor, whether it was actual contention during an outage or just an ill-placed Virtual Machine or Resource Pool Limit. Let’s play through an example:

A VM experienced a non-specified event (hint, it was a 2GB limit) and now about 14GB of its 16GB of allocated memory are swapped out to the default swap location.

# memstats -r vm-stats -u mb -s name:memSize:max:consumed:swapped | sed -n '/  \+name/,/ \+Total/p'
           name    memSize        max   consumed    swapped
-----------------------------------------------------------
      vm.449922      16384       2000       2000      14146

[Read more…] about I have memory pages swapped, can vSphere unswap them?

Here you go, VSAN 6.2 GA!

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We’ve been talking about if for a while now, but last night the moment finally arrived… VSAN 6.2 aka vSphere 6.0 Update 2 was released. I am not going to go in to any level of depth here, as I have written many posts on the subject of VSAN 6.2 already, and so has my friend Cormac, the best start is probably this blog though. You can read those if you want to get the nitty gritty details, or nerd knobs as apparently some like to call it. (I prefer to call it a healthy level of curiosity, but that is a different discussion.) Here is what is in 6.2:

  • Deduplication and Compression
  • RAID-5/6 (Erasure Coding)
  • Sparse Swap Files
  • Checksum / disk scrubbing
  • Quality of Service / Limits
  • In mem read caching
  • Integrated Performance Metrics
  • Enhanced Health Service

Now that is not it, there is also some new stuff in vSphere 6.0 Update 2, one which I feel is very welcome and that is the Host Client! A full HTML5 based client which comes as part of your ESXi host, very useful if you ask me! Also two-factor authentication was added for the Web Client, several enhancements to the vSphere APIs for IO Filtering and support for different databases for vCenter etc.

Okay, lets stop blabbing, start your download engines, find your bits here:

Awesome fling: ESXi Embedded Host Client

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A long long time ago I stumbled across a project within VMware which allowed you to manage ESXi through a client which was running on ESXi itself. Basically it presented an html interface for ESXi not unlike the MUI we had in the old days. It was one of those pet-projects being done in spare time by a couple of engineers which for various reasons at the time was never completed. The concept/idea however did not die fortunately. Some very clever engineers felt it was time to have that “embedded host client” for ESXi and started developing something in their spare time and this is the result.

I am not going to describe it in detail as William Lam has an excellent post on this great fling already. The installation is fairly straight forward, basically a vib you need to install. No rocket science. When installed you can manage various aspects of your hosts and VMs including:

  • VM operations (Power on, off, reset, suspend, etc).
  • Creating a new VM, from scratch or from OVF/OVA (limited OVA support)
  • Configuring NTP on a host
  • Displaying summaries, events, tasks and notifications/alerts
  • Providing a console to VMs
  • Configuring host networking
  • Configuring host advanced settings
  • Configuring host services

Is that cool or what? Head over to the Fling website and test it. Make sure to provide feedback when you have it as the engineers are very receptive and always looking to improve their fling. Personally I hope that this fling will graduate and will be added to ESXi by default, or at a minimum be fully supported! Excellent work Etienne Le Sueur and George Estebe!