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Snapshots

Automating The Creation Of Active Directory Snapshots:


Working with Active Directory Snapshots in Windows Server 2008:


Active Directory Domain Services Database Mounting Tool (Snapshot Viewer or Snapshot Browser) Step-by-Step Guide:
 
Reanimating Active Directory Tombstone Objects:


TS Session Broker
 
How does TS Session Broker work:
 
A closer look at Session Broker load balancing in Windows Server 2008:

DAS - SAN - NAS
 
NAS-SAN Comparison

DNS

Understanding Aging and Scavenging

Don't be afraid of DNS Scavenging. Just be patient.

MS DNS Dynamic Record Registration

What aging/scavenging do?

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DNS Scavenging can permit you to keep a "clean" DNS zone by deleting old records. "Old records" means DNS records that are obsolete for many days or week, not for hours...
Scanvenging is not really dynamic and won't delete a record as soon as it is unused... It will takes days before the record to be deleted.

Scavenging setting need at least two parameters (I'm not sure of english translation of these settings cause I'm using french version of Windows) :
 - The "refresh prohibit" period (7 days by default) : When a DNS record is created or refreshed, then it cannot be refreshed again (meaning the timestamp can nont be updated) for 7 days.
 - The "grace period before delete" (7 days by default) : If a DNS records is not refreshed for 7 days (meaning the timestamp is 7 days old) then it is deleted.

The first period ("refresh prohibit") is made to limit the numbre of AD object replication because with AD integrated DNS zones, DNS records are AD objects and then each timestamp refresh is an AD object modification. Dynamic DNS registration may then provocate too much object modification in AD. To avoid that, by default, a DNS record refuse new timestamp refresh for 7 days since the last refresh.

So, in fact, an unused DNS record will be deleted 14 days after it's last refresh if you configure scavenging with default settings (7 days + 7 days).

You can reduce these periods but don't expect for a really fast cleaning of the DNS zone. You can probably reduce periods to 3 days + 3 days. That will avoid DNS records to be deleted after the week-end.


In fact, may be you DHCP lease time is too short... 12 hours is very short. But it can be justified if you have a lot of external laptops that occasionally connect on your network. If not, you can probably increase the DHCP lease to some days... 4 days is a usually a good value.

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