VMware Raw Device Mapping (RDM) Volume, Detailed Material

An excellent post that is very informative on VMware Raw Device Mapping (RDM) volumes that explains what they are, the different between physical and virtual compatibility, when to use which and when not to use RDM’s at all:


So it’s basically a great post on everything you’ve wondered on RDM volumes.

I really appreciated this tidbit:

  • The maximum size of an RDM is 2TB minus 512 bytes.
  • Use the Microsoft iSCSI initiator and MPIO inside the VM when you need more than 2TB on a disk.

This is how I came across the above article. I was trying to figure out which method was better for presenting a large disk to a virtual machine – RDM vs iSCSI inside the VM. The above answered my question as it was a 3TB volume!

Also, here’s a great whitepaper from VMware discussing the performance differences between VMFS, RDM’s, etc. especially since this has changed quite a bit from ESX 3.5 to now (vSphere 4.x). The whitepaper is entitled “Comparison of Storage Protocol Performance in VMware vSphere 4”:

Symantec NetBackup – “File Write Failed”, Status 14, When Updating Master Server Properties

Possible Error – File Write Failed (14)


If you receive this error when using Windows 2008 or Windows 2008 R2:
Unable to save data on some hosts
An error occured on host <master>. The error is ‘file write failed (14)’.

You are probably experiencing Windows User Account Control (UAC) is not letting NetBackup save its information. The following technote describes how to address this issue, which we have also copied the workaround below.

Status 14 (file write failed) occurs when updating host properties on a Windows 2008 Master Server

This has been seen in cases where User Account Control (UAC) is enabled under Control Panel – User Accounts. This causes a logged in Administrator to run all programs with User-Level rights as opposed to Administrator-Level rights unless the user specifically requests to run an application with Administrator rights.

There are three workarounds:
1) If User Account Control is not required, disabling it may allow the host properties update to complete. This can present a risk to the OS and needs to be evaluated by the appropriate Windows Administrator.

2) In the short-term, to avoid this problem, you can manually launch the NetBackup Administration Console with Administrator rights by right-clicking on the icon and selecting "Run as administrator".

3) For long-term use, you can change the short-cut icon to always launch with Administrator rights by right-clicking on it, selecting Properties > Shortcut > Advanced and place a check in the box next to "Run as administrator".

VMware – Cannot Expand a VMFS Datastore on vSphere 4, Solution

I was at a customer site and was showing him how to expand the VMFS datastore on vSphere 4. Problem was however, it would not increase. If you clicked on the “Increase” button in the VMFS datastore’s properties, the next screen is supposed to show you the available “free” space left on that disk so you can use that free space to increase the VMFS size. However it was coming up blank.

I found a post that said to try and connect directly to an ESX/vSphere server and try the vmfs increase that way, as they were having the same problem. There are several posts from people (eg: http://communities.vmware.com/thread/220476?start=15&amp;tstart=0)who that method worked for, even when it wouldn’t work when connecting to vCenter, like I experienced. So I had the customer try that method and it worked!

Here’s the other thread I found:

VMware – vSphere 4.1 Handy and Useful Links

Scott Lowe has posted an awesome collection of vSphere 4.1 links, which he’s shared here:

I’m also posting below for reference on our site (in no particular order):
vSphere 4.1 – The First Bug found (and how to resolve it) « Itzikr’s Blog
VMware KB: ESX/ESXi installations on HP systems require the HP NMI driver
VIDEO: New vSphere 4.1 Windows Active Directory Authentication
What’s New in vSphere 4.1
vSphere 4.1 Storage Networking Updates « Wikibon Blog
VMware Communities: VMware In SMB: ESXi Scripted Installation Via PXE and Kickstart!
Support Insider: Useful vSphere 4.1 Knowledgebase Articles
VMware: VMTN Blog: vSphere 4.1 and more
VMware: VMware vSphere Blog: vSphere 4.1 is Here! Tell Me Something About the Release I May Not Know
Welcome to vSphere-land! » Tidbits on the new vSphere 4.1 release
vSphere 4.1, VMware HA New maximums and DRS integration will make our life easier
VMware KB: Setting the number of cores per CPU in a virtual machine
VMware KB: Changes to Fault Tolerance in vSphere 4.1
A Few Gotchas With vSphere 4.1! | Daily Hypervisor
VMware: Uptime (VMware and Business Continuity): VDR and vSphere 4.1 compatibility
VMware KB: Changes to VMware High Availability in vSphere 4.1
Blue Gears » Blog Archive » vSphere Upgrade: Going to 4.1
Stuff: PAM changes in ESX 4.1
Krystaltek: DRS/Fault Tolerance Placement Restrictions
Don’t add resource pools for fun, they’re dangerous – NTPRO.NL – Eric Sloof
How to use vMA 4.1 installation, configuration « GeekSilver’s Blog
Two new HA Advanced Settings » Yellow Bricks
DRS 4.1 Adaptive MaxMovesPerHost | frankdenneman.nl
vSphere 4.1 to 4.0 differences
VMware vSphere 4.1: Not the Typical .1 Release
VMware KB: VMware ESX and ESXi 4.1 Comparison
Best practices KB on how-to install ESX 4.1 and vCenter | ESX Virtualization
VMware KB: Copy and Paste option is disabled in vSphere Client 4.1

VMware – Best Practice KB Articles for Installing vSphere 4.1 and vCenter 4.1

Here’s a great post over at www.vladan.fr (who’s a well known VMware blogger and vExpert) on some of the KB articles he’s found regarding best practices on installing vSphere 4.1 and vCenter 4.1.

Preparing the vCenter Server Installation Worksheet – Download and fill out the vCenter Server Installation Worksheet.
MicrosoftSQL Server 2005 Express is intended for use with small deployments of up to 5 hosts and/or 50 virtual machines.

    Memory – 3GB RAM. RAM requirements may be higher if your database runs on the same machine. VMware VirtualCenter Management WebServices requires 128Mb to 1.5GB of memory which is allocated at startup.Disk storage – 2GB. Disk requirements may be higher if your database runs on the same machine.

  • vCenter Server 4.1 requires a 64 bit DSN and MUST NOT be a Domain controller. vSphere Compatibility Matrix.
  • The computer name – no more than 15 characters.
  • have reliable DNS and Time services.

Recommended, but not mandatory:

  • separate database for vCenter Server and vCenter Update Manager

vCenter server needs all this (will be installed as part of vCenter Installation):

  • Apache Tomcat (64 bit)
  • Java Runtime Environment JRE (64 bit)
  • Active Directory Application Management (ADAM)
  • Visual C++ 2005 Runtime Redistributable
  • .NET 3.0 SP1 or above (optional based on DB selection)

If the machine on which you are installing vCenter Server has a previous version of vCenter installed (if it’s on 64 bit hardware), you might want to upgrade instead of performing a fresh installation of vCenter Server.

Best practices for the ESX installations:

Check on the HCL (hardware compatibility list) page…. – I blogged about that earlier too ….

  • System compatibility
  • I/O compatibility (Network and HBA cards)
  • Storage compatibility
  • Backup software compatibility

32bits installation are no longer supported. VMware ESX 4.1 only installs and runs on servers with 64 bit x86 CPUs.

  • Check the Enable Intel VT in the BIOS.
  • If you are installing to the local disks and you have a  SAN with Fiber Channel connected  to the ESX host, make sure and detach the fiber before continuing with the installation. (Do not disable HBA cards in the BIOS)
  • minimum size of the vmdk where the  /swap, and all the optional partitions are stored should be set for 8GB.
  • Make a separate partition for  /var/log.

Source: Installing ESX 4.1 and vCenter Server 4.1 best practices