Unable to acquire lease on server. Waiting... when running a Clearwell Enterprise Vault Collection Task

Problem

An eDiscovery Platform (eDP) Enterprise Vault(EV) Collection Task requires access to the Enterprise Vault environment for two stages; the first stage is the search of indexes for qualified items; the second is to retrieve those items (Content Retrieval).
 
When running multiple EV Collection Tasks, only one task can control the Index Search or the Content Retrieval processes at any given moment.  Additional EV Collection Tasks are queued at the requested process (Index Search or Content Retrieval).

Once the process is completed by the current Task, the next Collection Task in queue will receive the lease on the server for that process.

EXAMPLE:
a) EV Collection Task 1 and 2 and 3 are started, one after another.  Task 1 acquires the lease for the Index Server on the EV server; Task 2 and 3 are queued for the Index Server with 'Unable to acquire lease on server. Waiting...'. 

b) Once Task 1 completes the Search, it releases the lease on the Index Search and acquires the lease for the Content Retrieval process (StorageOnlineOpns).  Task 2 acquires the Search Index lease and Task 3 continues to wait for a lease.

c) Once Task 2 completes the search portion and Task 1 is still in Content Retrieval mode, Task 2 releases the Search Index lease and goes back to 'Unable to acquire lease on server. Waiting...' for the Content Retrieval lease.  Task 3 begins its lease on the Search Index process.
 
d) This process continues until all tasks are complete.

Note:
A Task will fail if a lease cannot be acquired within 60 minutes upon entering the queue.

Solution

An Index Search is memory intensive and Content retrieval or Export, is CPU and memory intensive.  Having multiple EV Collection Tasks running will have an adverse affect on the EV daily operations.  The eDP is designed to not overwhelm an EV environment with more than one Index Search and one Content Retrieval at any given point.

Schedule the EV Collection Tasks far enough apart to virtually eliminate or reduce the need for a Task to wait on an EV lease.

Note:
- If running more than one eDP Collection appliance, it is recommended to add the following registry entry on EV environments that contain 32-bit indexes (EV version 9 indexes and EV version 10 prior version indexes).  The registry key prevents more than thirty IndexServer processing threads to be launched on the EV Indexing Server. 

Warning: Incorrect use of the Windows registry editor may prevent the operating system from functioning properly. Great care should be taken when making changes to a Windows registry. Registry modifications should only be carried-out by persons experienced in the use of the registry editor application. It is recommended that a complete backup of the registry and workstation be made prior to making any registry changes.

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\KVS\Enterprise Vault\Indexing  (Windows Server 2008 R2)
HKEY_LOCAL_MACHINE\SOFTWARE\KVS\Enterprise Vault\Indexing (Windows Server 2003)

Dword: MaxIndexServer
Value: 30 (decimal)

-- The EV Indexing Service will need to be restarted for the registry key to take effect.