Z Nos & facts


1. GPO is refreshed every 90 minutes

2. Universal Group Membership Caching (UGMC) is refreshed every 8 hrs

3. Clients and DC time should not be more than 5 minutes. Otherwise user cannot login to the clients via Domain

4. Once a change is happened on a Domain Controller (Active Directory Database) and if there is no additioanl change for the next for 5 minutes, DC will replicate the changes to other DCs. If there are multiple DCs then the replication will happen in 30 seconds gap.

KCC is a built-in process in Domain controllers that performs the replication, responsible for establishing replication topology. KCC is responsible for setting up replication between Bridge head servers. KCC selects the Bridge head servers.

5. DHCP lease duration:

Minimum: We can set from 15 Minutes

Default: 8 days

Maximum: Around 1000 days


1. AD database location is C:\Windows\NTDS\ and the database name is ntds.dit

2. Each domain controller in an Active Directory forest can create a little bit less than 2.15 billion objects during its lifetime.

3. We can apply maximum of 999 Group policies to an object / OU in AD

More info: There is a limit of 999 Group Policy objects (GPOs) that you can apply to a user account or computer account. This does not mean that the total number of policy settings on the system is limited to 999. Rather, a single user or computer will not be able to process more than 999 GPOs. This limit exists for performance reasons.

4. Fully qualified domain names (FQDNs) in AD cannot exceed 64 characters in total length, including hyphens and periods.

5. NetBIOS computer and domain names are limited to 15 characters.

6. Domain Name System (DNS) host names are limited to 24 characters.

7. OU names are limited to 64 characters.

8. Max recommended Users per group in AD:

Windows 2000: 5000 users

Windows 2003: 500 million (Forest functional level should be atleast Windows 2003 Interim)

Windows 2008: 500 million

9. Recommended Maximum Number of Domains in a Forest

Windows 2000: 800

Windows 2003: 1200

Windows 2008: Not available

10. Recommended Maximum Number of Domain Controllers in a Domain

Windows 2000: 1200

Windows 2003: 1200

Windows 2008: 1200

11. Windows drive size limitations

Current BIOS supports only MBR and not GPT. Hence booting drive needs to be MBR only.

  • FAT32 file systems have a maximum volume size of 32GB with a file size limit of 4GB.
  • NTFS volumes can be up to 2TB on an MBR disk and 16 Exabytes (EB) on GPT disks.
  • The maximum size NTFS volume that has been tested by Microsoft is 16 TB.

Windows 2003, 2008 – 2TB per drive for Basic disks

Windows 2003, 2008 –

  • Up to 64 TB for spanned and striped volumes.
  • Up to 62 TB for RAID-5 volumes. 2 TB used for parity.

12. Drives larger than 2TB, we should use GPT and not MBR type partition.


13. Windows 2008 R2 is only available with 64 bit. All other Windows OSes are available with both 32 and 64 bit.

Fore more details:


14. Windows passwords can be upto 127 characters long. This is not applicable for Windows 95 and 98.



Difference between:


Windows 2003 vs Windows 2008

Windows 2008 has Server core functionality (CLI based OS)
WDS instead of RIS
Services have been changed as roles – server manager
Introduction of hyper V- only on 64 bit versions
Enhanced event viewer
Bitlocker feature
MMC 3.0, with three pane view
Key management services(KMS) to activate Windows OS without connecting to Microsoft site
Performance enhancement using technologies like Windows SuperFetch,ReadyBoost and Readydrive
Windows Aero user interface
Instant search
Support for IPv6 in DNS


ESXi has no service console which is a modified version of RHEL
ESXi is extremely thin hence results in fast installation + fast boot
ESXi can be purchased as an embedded hypervisor on hardware
ESXi has builtin server health status check

ESXi 4.1 vs ESXi 5.0 – Migration

Local upgrade from CD
VMware update manager (only supports upgrade of ESX/ESXi 4.x to ESXi 5.0)

ESXi 4.1 vs ESXi 5.0 – Features

vSphere Auto deploy
Storage DRS
HA – Primary/secondary concept changed to master/slave
Profile driven storage
VMFS version – 3 → 5
ESXi firewall
VMware hardware version – 7 →  8
VMware tools version – 4.1 → 5
vCPU – 8 → 32
vRAM – 256 → 1 TB
VMs per host – 320 → 512
RAM per host – 1TB → 2TB
USB 3.0 support


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