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© Rakhesh Sasidharan

vSphere Replication does not support changing the length of a replicated disk.

Had to extend a VM disk today and got the above error. This is because the VM is replicated via vSphere Replication so you can’t simply extend the disk as you would do for any regular VM.


Here’s a top level summary of how you do it (based on this KB article).

  1. You have to break the replication. Stop it that is. But doing so deletes the replicated files, so first you want to work around that (as below).
    1. Note the current settings of the replication.
    2. Then pause the replication.
    3. Find out which datastore holds the replicated VM disks.
    4. Rename the replicated VM folder.
    5. Now you can stop the replication because you have kept a copy of the data.
  2. SSH into any ESX host that has access to the above datastore and extend the disk associated with the VMDK via vmkfstools.
  3. Rename the folder back to what it was before.
  4. Recreate the replication, but point the destination to the same datastore as above and select the folder above. vSphere Replication will ask whether you want to use the existing data as seed – answer yes.

That’s it basically.

In terms of the details, I didn’t know how to find which datastore had the replicated VM files. So I SSH’d into one of the hosts in the replicated VM cluster and ran the following:

There must be some better way, but what the heck. Once I found the path above I did the following to find other VMs in it, and using that info I was able to find the datastore name from vSphere client.

You need this datastore name for when setting up a new replication, so you can point to that.

Some more things to keep in mind are the following.

  1. Since we pause the replication rather than stop it, the folder will contain a bunch of hbr* files. Delete those.
  2. The vmkfstools command -X switch takes the new size of the disk. Not the additional amount. So if the disk is 10GB and you want to add 20GB, you specify it the argument as 30GB. If you are getting a “Failed to extend disk : One of the parameters supplied is invalid (1).” error with vmkfstools that’s probably why.

Install a vSphere web-client plugin offline

Trying out vCloud Air at work and I wanted to install the vCloud Air plugin for vSphere web-client. The installation kept failing though. Initially it was due to the vCenter server not having access to the Internet (not your browser, the vSphere web-client itself needs to have access) but even after I specified a proxy (check out this post on how to specify a proxy) and gave vSphere web-client access to the Internet the download would begin and fail. 


It’s possible to download the plugin, but how to add it to vSphere web-client?

Through a bit of trial and error I found a way. :)

Turns the plugins are store at C:\Program Files\VMware\Infrastructure\vSphereWebClient\plugin-packages on the server. So all you have to do is:

  1. Download the plugin zip file. 
  2. Create a folder in the above location and extract the zip file to this folder.
  3. Restart the vSphere web-client service. 

And that’s it! Then your plugin will appear under Administration > Client Plug-Ins


It’s very simple but I couldn’t find any info on how to download and install a plugin when I Googled for it, so thought I’d make a post. Hope it helps someone!

vCenter and vSphere editions (5.5)

vCenter editions. Just three.

  • Essentials
  • Foundation
  • Standard

Standard is what you usually want. No limits or restrictions.

Essentials is only available when purchased as part of vSphere Essentials or vSphere Essentials Plus kits. Not sold separately. These kits are targeted for SMBs. Limited to 3 hosts of 2 CPUs each. Self-contained – cannot be used with other editions.

Foundation is also for 3 hosts only.

All editions of vCenter include the Management service, SSO, Inventory service, Orchestrator, Web client – everything. There’s no difference in the components included in each edition.

vSphere is the suite. There are three plus two edition of vSphere suite.

Two editions are the kits:

  • Essentials
  • Essentials Plus

Three editions are bundled with vCenter Operations Manager:

  • Standard
  • Enterprise
  • Enterprise Plus

The Essentials & Essentials Plus editions only work with vCenter Essentials. The Standard, Enterprise, and Enterprise Plus work with vCenter Foundation or Standard.

Essentials is pretty basic. Remember it is for 3 hosts of 2 CPUs each. Standalone. In addition you don’t get features like vMotion either. All you get is (1) Thin Provisioning, (2) Update Manager, and (3) vStorage APIs for Data Protection (VADP). Note the latter is only APIs. It is not VMware solution vSphere Data Protection (VDP). Also, no VSAN.

Essentials Plus is a bit more than basic. Once again, only for 3 hosts of 2 CPUs each. Standalone. However, in addition to the three features above you also get (4) vSphere Data Protection, (5) High Availability (HA), (6) vMotion, and (7) vSphere Replication. So you get some useful features. In fact, if I had just 3 hosts and I am unlikely to expand further this is the option I would go for – for me vMotion is very useful and so is HA. Sadly, no Distributed Resource Scheduling (DRS). But you do get VSAN.

Moving on to the big boys …

Standard gives you all the above plus useful features like (8) Storage vMotion, (9) Fault Tolerance, and some more (Hot Add & vShield Endpoint). Still no DRS.

Enterprise gives you all the above plus (10) Storage APIs for Array Integration (nice! but useful only in an Enterprise context where you are likely to have a SAN array and need something like this), (11) DRS, (12) DPM, and (13) Storage APIs for Multi-pathing. As expected, features that are more useful when you have a lot of hosts and are in an Enterprise-y setup. Except DRS :) which would have been nice to have in Standard/ Essentials Plus too.

Finally, Enterprise Plus. All the above plus (13) Distributed Switches, (14) Host Profiles, (15) Auto Deploy, (16) Storage DRS – four of my favorite features – and a bunch of others like App HA, Storage IO Control, Network IO Control, etc.

vSphere 5.5 Maximums

This document contains all the vSphere 5.5 maximums. Here are some of the figures for my quick reference:

Hosts per vCenter Server (Appliance)(embedded vPostgres database)100
VMs per vCenter Server (Appliance)(embedded vPostgres database)3000
Hosts per vCenter Server (Appliance)(Oracle database)1000
VMs per vCenter Server (Appliance)(Oracle database)10000
Hosts per vCenter Server (Windows)(bundled SQL Server Express database)5
VMs per vCenter Server (Windows)(bundled SQL Server Express database)50
Hosts per vCenter Server (Windows)(external database)1000
VMs per vCenter Server (Windows)(external database)10000

So the Windows install with inbuilt database is the lowest of the lot. You are better of going with the appliance (which has its own limitations of course). 

Maximums of appliance and Windows server are the same as long as they use an external database. But appliance can only use Oracle as an external database while Windows server can use SQL too.

VMware: “A specified parameter was not correct” error

Was trying to delete a VM template but it kept throwing the above error. I had a feeling this was because the underlying disk was missing in the datastore (because I couldn’t find any folder with the same name as the VM in the datastore) but there was no way to confirm this as you can’t right click a VM and note its settings.

Thanks to PowerCLI though, you can:

The Get-HardDisk cmdlet can be used to return the hard disks used by a VM or template. It can even be used to return all hard disks on a datastore (or in a specified path on the datastore):


PowerCLI – List all VMs in a cluster along with number of snapshots and space usage

More as a note to myself than anyone else, here’s a quick and dirty way to list all the VMs in a cluster with the number of snapshots, the used space, and the provisioned space. Yes you could get this information from the GUI but I like PowerShell and am trying to spend more time with PowerCLI.


[Aside] Hyper-V R2 replicas

Saw this post in the Technet newsletter. Good stuff. I won’t be using it now (wish I were managing a Hyper-V environment in the first place! setting up replicas is a far away dream L:)) but thought I should point to it anyways. Maybe some day I’ll need to use Hyper-V replicas and I’ll search my blog and come across this … maybe maybe! :)

From my ESXi training I know VMware has something similar (vSphere Replication). The latter is a paid additional feature while Hyper-V replicas are free. Also, here’s a comparison by Aidan Finn.