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.
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Vmware hostd and vpxa on ESXi 5.X
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 vpxa service
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).
- vpxa is the VC agent (ESX side)
- vpxd is the VC daemon (VC side)