What is hostd and vpxa ?

hostd is an app that runs in the Service Console that is responsible for managing most of the operations on the ESX machine.  It knows about all the VMs that are registered on that host, the luns/vmfs volumes visible by the host, what the VMs are doing, etc.  Most all commands or operations come down from VC through it.  i.e, powering on a VM, VM vMotion, VM creation, etc.

vpxa also runs on the Service Console and talks to VC.  I believe it acts as an intermediary between VC and hostd. I think it also does some housekeeping on the ESX host, but not as much as hostd.

Courtesy : http://vmaze.wordpress.com/

 

Vmware hostd and vpxa on ESXi 5.X

HOSTD

The vmware-hostd management service is the main communication channel between ESX/ESXi hosts and VMkernel. If vmware-hostd fails, ESX/ESXi hosts disconnects from vCenter Server/VirtualCenter and cannot be managed, even if you try to connect to the ESX/ESXi host directly. It knows about all the VMs that are registered on that host, the luns/vmfs volumes visible by the host, what the VMs are doing, etc. Most all commands or operations come down from VC through it. i.e, powering on a VM, VM vMotion, VM creation, etc.

Restart the management agent

/etc/init.d/hostd restart

VPXA

It acts as an intermediary between VC and hostd. The vCenter Server Agent, also referred to as vpxa or the vmware-vpxa service, is what allows a vCenter Server to connect to a ESX host. Specifically, vpxa is the communication conduit to the hostd, which in turn communicates to the ESX kernel.

Restart the vpxa service

/etc/init.d/vpxa restart

 

Note:- If you have SSH enabled on your ESXi server these services can also be restarted and even if these are restarted by you then also your SSH session will not be impacted.

VPXD-It is Vcenter Server Service. If this service is stopped then we will not able to connect to Vcenter Server via Vsphere client.

VPXA-It is the agent of Vcenter server. also known as mini vcenter server which is installed on the each esx server which is managed by Vcenter server. What are the management action we are performing on top of the vcenter server. (Like:- Increasing/Decreasing RAM & HDD, Making any type of changes in cluster, doing vmotion. This agent collects all information from the vcenter server and pass this information to the kernal of the esx server.

HOSTD- This is the agent of ESX server, here VPXA pass the information to the HOSTD and hostd pass the information to ESX server.

In ESX, you have only hostd and (if you have vCenter) vpxa.

These are daemon (services) for remote management:

• hostd is used to remote management using VIC
• vpxa is used by vCenter (the vpxd part of vCenter) to remote manament

hostd is the daemon for direct VIC connection (when you use Virtual Infra Client (VIC) to connect to your ESX).

Also,

• vpxa is the VC agent (ESX side)
• vpxd is the VC daemon (VC side)