vSphere New Feature " FT "

HA, or High Availability is to ensure that if one of your hosts dies (poof, gone, power failure, hardware failure, network failure, etc) vCenter will detect the failure and then take the VM's that used to be running on the host that failed, and power up on another host in the cluser. What used to happen prior to HA was that if your host went down, those VM's were down until you repaired the host or manually registered them on another host and powered them up. HA powers them up automatically in the event of a host failure.
FT, or fault tolerance takes the concept of HA to a new level. Setting FT on a VM causes a standby VM to be setup. That VM is updated constantly so that in the case of a host failure, the standby VM immediately assumes processing. So, from a host OS perspective there is no power failure. The transition from primary FT VM to standby FT VM is nearly instantaneous. This ensures that there is no downtime for the FT VM.

Memory limits for VMware products

vSphere4 & 4.1

The Machine SID Duplication Myth

An article by Mark Russinovich specifying why New SID is irrelevent :

The reason that I began considering NewSID for retirement is that, although people generally reported success with it on Windows Vista, I hadn’t fully tested it myself and I got occasional reports that some Windows component would fail after NewSID was used. When I set out to look into the reports I took a step back to understand how duplicate SIDs could cause problems, a belief that I had taken on faith like everyone else. The more I thought about it, the more I became convinced that machine SID duplication – having multiple computers with the same machine SID – doesn’t pose any problem, security or otherwise. I took my conclusion to the Windows security and deployment teams and no one could come up with a scenario where two systems with the same machine SID, whether in a Workgroup or a Domain, would cause an issue. At that point the decision to retire NewSID became obvious.

http://blogs.technet.com/b/markrussinovich/archive/2009/11/03/3291024.aspx

Patching ESX Server

Patching ESX Server
At the time of writing, patch version 27728 was the latest update for ESX Server 2.5.3. The patch process is generally similar for 2.5.x patches.
Proceed as follows:

1. Determine the Patch Revision from the Host SW Manifest tab of the PID.
2. Obtain the TAR archive containing the update from the Vmware website.
3. Power off all virtual machines and shutdown your server.
4. Restart your system.
5. At the LILO Boot Menu, select linux UP (linux Uniprocessor.)
6. Allow the system start procedure to complete.
7. Log in as root into the ESX Server service console, in Linux mode. Make sure your path variable contains /usr/bin:/bin.
8. Download the tar file into the temporary directory /tmp on the service console.
9. Change directories to /tmp.
10. Extract the compressed tar archive:
# tar -xvzf esx-2.5.3-27728-upgrade.tar.gz
11. Change directories to the newly created directory /tmp/esx-2.5.3-27728-upgrade:
# cd esx-2.5.3-27728-upgrade
12. Run the installer:
# /usr/bin/perl ./upgrade.pl
13. The system updates have now been installed. A reboot prompt displays:
Reboot the server now [y/n]?

For Loop to Process Multiple Files in a Folder

To register all the files in the System32 folder, type the following command and press ENTER:

for %m in (*.dll) do regsvr32 /s %m

Name Resolution

If all of these name resolution methods are used, an h-node host computer implements them in the following order:
NetBIOS name cache
WINS server
B-node broadcast
LMHOSTS file
HOSTS file
DNS server

SUBST

Allows you to substitute a folder on your computer for another drive letter.

SYNTAX
Associates a path with a drive letter.
SUBST [drive1: [drive2:]path]SUBST drive1: /D
drive1: Specifies a virtual drive to which you want to assign a path. [drive2:]path Specifies a physical drive and path you want to assign to a virtual drive. /D Deletes a substituted (virtual) drive.
Type SUBST with no parameters to display a list of current virtual drives.

EXAMPLES
SUBST a: . Sets the directory you are in and subdirectories thereafter into the A: drive. So if you were to type A: after doing this command you would see everything in the directory that you typed this command in.
If you were to reboot your computer this will clear the SUBST command and put your drives back to original letters (unless command placed into the autoexec.bat).
You cannot subst network drives.