Load Balancing Session Placement Examples

These examples illustrate two load balancing session placement scenarios.

Example 1: No Existing User Session

This example illustrates how session placement might occur for a farm that contains six RDS hosts when a user session does not currently exist on any of the RDS hosts.

1. Horizon Agent reports the following load preferences for each RDS host in the farm.

   RDS Host	Load Preference
   1	HIGH
   2	LOW
   3	HIGH
   4	MED
   5	BLOCK
   6	LOW

2. View sorts the RDS hosts into three buckets according to load preference. View discards RDS host 5 because Horizon Agent reported a load preference of BLOCK.

   Bucket	Load Preference	RDS Host
   1	HIGH HIGH	1 3
   2	MED	4
   3	LOW LOW	2 6

3. Because bucket 2 has only one RDS host, View combines bucket 2 and bucket 3

   Bucket	Load Preference	RDS Host
   1	HIGH HIGH MED	1 3 4
   2	LOW LOW	2 6

4. View randomizes the bucket order.

   Bucket	Load Preference	RDS Host
   1	MED HIGH MED	4 3 1
   2	LOW LOW	6 2

5. View Connection Server attempts to place a new application session on RDS host 4 first, followed by RDS host 3, and so on.

   RDS Host Session Placement Order
   4
   3
   1
   6
   2

   Note:

   Anti-infinity rules can prevent an application from being placed on an RDS host, regardless of the reported load preference. For more information, see Configure an Anti-Affinity Rule for an Application Pool.

Example 2: Existing User Session

This example illustrates how session placement might occur for a farm that contains six RDS hosts when a user session currently exists on one of the RDS hosts. An RDS host that contains a session in which a user has previously run an application is always reused for the same application.

1. A user session already exists on RDS host 3. RDS host 3 has a load preference of MED. The remaining RDS in the hosts in the farm (the spare list) have the following load preferences.

   RDS Host	Load Preference
   1	MED
   2	LOW
   4	HIGH
   5	LOW
   6	BLOCK

2. View sorts the RDS hosts in the spare list into two buckets according to load preference. View discards RDS host 6 because Horizon Agent reported a load preference of BLOCK.

   Bucket	Load Preference	RDS Host
   1	HIGH MED	4 1
   2	LOW LOW	2 5

3. View randomizes the bucket order.

   Bucket	Load Preference	RDS Host
   1	HIGH MED	4 1
   2	LOW LOW	5 2

4. View adds the RDS host that contains the existing session to the top of the new bucket ordered list.

   RDS Host Session Placement Order
   3
   4
   1
   5
   2