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PostgreSQL and PgBouncer Sizing and Configuration Guide

KB ID: 4758
Product: Veeam Backup for Microsoft 365 | 8.1 | 8.2
Published: 2025-08-19
Last Modified: 2025-12-03
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Challenge

Jobs or tasks in Veeam Backup for Microsoft 365 fail with the error:

Error: [EFCoreLogging]: An error occurred using the connection to database 'cache_2331ace3-eff1-4ebb-b328-0cb948b2f5c5' on server 'tcp://vb365.domain.tld:6432'.

Cause

These connection errors can occur in larger environments when many proxies and repositories attempt to communicate with their respective cache databases concurrently. The cumulative concurrent connections can overwhelm the PostgreSQL instance.

Solution

Based on extensive testing, Veeam's RND team has found that using PgBouncer in larger environments (as detailed in the table below) to pool connections can improve communication efficiency and resolve related errors.

Please follow the steps in KB4728: How to Install and Configure PgBouncer for Veeam Backup for Microsoft 365, and refer to the table below for configuration recommendations based on environment size.

Note: Each row can be expanded to reveal a SQL query that should be executed on the PostgreSQL instance to optimize its configuration.

Follow the recommendation that corresponds to the higher value between proxy count and repository count. For instance, if an environment has 15 Proxies and 260 Repositories, or 30 Proxies and 100 Repositories, select the option for "25 to 100" proxies and "greater than 250" repositories.
  Proxies per VB365 Server Repositories per VB365 Server PostgreSQL Deployment Location PostgreSQL Minimum
Resources		 PgBouncer Recommendation
  1 to 10 less than 100 PostgreSQL on VB365 Server 8 vCPU | 32 GB PgBouncer should not be deployed
  Query to Set Recommended PostgreSQL Configuration Values Adjusted PgBouncer Values
  
ALTER SYSTEM SET max_connections = '1000';
ALTER SYSTEM SET checkpoint_timeout = '1200';
ALTER SYSTEM SET effective_cache_size = '12GB';
ALTER SYSTEM SET checkpoint_completion_target = '0.9';
ALTER SYSTEM SET wal_buffers = '16MB';
ALTER SYSTEM SET wal_level = 'minimal';
ALTER SYSTEM SET max_wal_senders = '0';
ALTER SYSTEM SET default_statistics_target = '100';
ALTER SYSTEM SET random_page_cost = '1.1';
ALTER SYSTEM SET max_worker_processes = '6';
ALTER SYSTEM SET max_parallel_workers_per_gather = '2';
ALTER SYSTEM SET max_parallel_workers = '4';
ALTER SYSTEM SET max_parallel_maintenance_workers = '2';
ALTER SYSTEM SET min_wal_size = '2GB';
ALTER SYSTEM SET max_wal_size = '8GB';
ALTER SYSTEM SET default_toast_compression = 'lz4';
ALTER SYSTEM SET wal_compression = 'lz4';
ALTER SYSTEM SET max_locks_per_transaction = '128';
ALTER SYSTEM SET hash_mem_multiplier = '2';
ALTER SYSTEM SET log_temp_files = '10MB';
ALTER SYSTEM SET log_lock_waits = 'on';
ALTER SYSTEM SET join_collapse_limit = '10';
ALTER SYSTEM SET geqo_threshold = '10';
ALTER SYSTEM SET log_line_prefix = '%m [%p] %q[user=%u,db=%d,app=%a] ';
ALTER SYSTEM SET jit = 'off';
ALTER SYSTEM SET log_autovacuum_min_duration = '1min';
ALTER SYSTEM SET log_min_duration_sample = '1s';
ALTER SYSTEM SET log_statement_sample_rate = '0.01';
ALTER SYSTEM SET log_filename = 'postgresql-%d-%H%M.log';
ALTER SYSTEM SET log_rotation_age = '4h';
ALTER SYSTEM SET log_rotation_size = '0';
ALTER SYSTEM SET log_truncate_on_rotation = 'on';
ALTER SYSTEM SET log_parameter_max_length = '10kB';
ALTER SYSTEM SET shared_buffers = '4GB';
ALTER SYSTEM SET maintenance_work_mem = '500MB';
ALTER SYSTEM SET work_mem = '8MB';
ALTER SYSTEM SET autovacuum_vacuum_cost_limit = '2000';
ALTER SYSTEM SET autovacuum_max_workers = '4';
ALTER SYSTEM SET huge_pages = 'off';

Not applicable as pgBouncer is not required.
  10 to 25 less than 250 Dedicated PostgreSQL Server 8 vCPU | 32 GB PgBouncer is required
  Query to Set Recommended PostgreSQL Configuration Values Adjusted PgBouncer Values
  
ALTER SYSTEM SET max_connections = '2000';
ALTER SYSTEM SET checkpoint_timeout = '1200';
ALTER SYSTEM SET effective_cache_size = '24GB';
ALTER SYSTEM SET checkpoint_completion_target = '0.9';
ALTER SYSTEM SET wal_buffers = '16MB';
ALTER SYSTEM SET wal_level = 'minimal';
ALTER SYSTEM SET max_wal_senders = '0';
ALTER SYSTEM SET default_statistics_target = '100';
ALTER SYSTEM SET random_page_cost = '1.1';
ALTER SYSTEM SET max_worker_processes = '6';
ALTER SYSTEM SET max_parallel_workers_per_gather = '2';
ALTER SYSTEM SET max_parallel_workers = '4';
ALTER SYSTEM SET max_parallel_maintenance_workers = '2';
ALTER SYSTEM SET min_wal_size = '2GB';
ALTER SYSTEM SET max_wal_size = '8GB';
ALTER SYSTEM SET default_toast_compression = 'lz4';
ALTER SYSTEM SET wal_compression = 'lz4';
ALTER SYSTEM SET max_locks_per_transaction = '128';
ALTER SYSTEM SET hash_mem_multiplier = '2';
ALTER SYSTEM SET log_temp_files = '10MB';
ALTER SYSTEM SET log_lock_waits = 'on';
ALTER SYSTEM SET join_collapse_limit = '10';
ALTER SYSTEM SET geqo_threshold = '10';
ALTER SYSTEM SET log_line_prefix = '%m [%p] %q[user=%u,db=%d,app=%a] ';
ALTER SYSTEM SET jit = 'off';
ALTER SYSTEM SET log_autovacuum_min_duration = '1min';
ALTER SYSTEM SET log_min_duration_sample = '1s';
ALTER SYSTEM SET log_statement_sample_rate = '0.01';
ALTER SYSTEM SET log_filename = 'postgresql-%d-%H%M.log';
ALTER SYSTEM SET log_rotation_age = '4h';
ALTER SYSTEM SET log_rotation_size = '0';
ALTER SYSTEM SET log_truncate_on_rotation = 'on';
ALTER SYSTEM SET log_parameter_max_length = '10kB';
ALTER SYSTEM SET shared_buffers = '8GB';
ALTER SYSTEM SET maintenance_work_mem = '500MB';
ALTER SYSTEM SET work_mem = '8MB';
ALTER SYSTEM SET autovacuum_vacuum_cost_limit = '2000';
ALTER SYSTEM SET autovacuum_max_workers = '10';
ALTER SYSTEM SET huge_pages = 'try';

When using Proxy Pools:

Set the following values in pgbouncer.ini:

default_pool_size = 100
max_user_connections = 1800
  25 to 100 greater than 250 Dedicated PostgreSQL Server 16 vCPU | 64 GB PgBouncer is required
  Query to Set Recommended PostgreSQL Configuration Values Adjusted PgBouncer Values
  
ALTER SYSTEM SET max_connections = '2200';
ALTER SYSTEM SET checkpoint_timeout = '1200';
ALTER SYSTEM SET effective_cache_size = '48GB';
ALTER SYSTEM SET checkpoint_completion_target = '0.9';
ALTER SYSTEM SET wal_buffers = '16MB';
ALTER SYSTEM SET wal_level = 'minimal';
ALTER SYSTEM SET max_wal_senders = '0';
ALTER SYSTEM SET default_statistics_target = '100';
ALTER SYSTEM SET random_page_cost = '1.1';
ALTER SYSTEM SET max_worker_processes = '16';
ALTER SYSTEM SET max_parallel_workers_per_gather = '2';
ALTER SYSTEM SET max_parallel_workers = '12';
ALTER SYSTEM SET max_parallel_maintenance_workers = '2';
ALTER SYSTEM SET min_wal_size = '2GB';
ALTER SYSTEM SET max_wal_size = '8GB';
ALTER SYSTEM SET default_toast_compression = 'lz4';
ALTER SYSTEM SET wal_compression = 'lz4';
ALTER SYSTEM SET max_locks_per_transaction = '128';
ALTER SYSTEM SET hash_mem_multiplier = '2';
ALTER SYSTEM SET log_temp_files = '10MB';
ALTER SYSTEM SET log_lock_waits = 'on';
ALTER SYSTEM SET join_collapse_limit = '10';
ALTER SYSTEM SET geqo_threshold = '10';
ALTER SYSTEM SET log_line_prefix = '%m [%p] %q[user=%u,db=%d,app=%a] ';
ALTER SYSTEM SET jit = 'off';
ALTER SYSTEM SET log_autovacuum_min_duration = '1min';
ALTER SYSTEM SET log_min_duration_sample = '1s';
ALTER SYSTEM SET log_statement_sample_rate = '0.01';
ALTER SYSTEM SET log_filename = 'postgresql-%d-%H%M.log';
ALTER SYSTEM SET log_rotation_age = '4h';
ALTER SYSTEM SET log_rotation_size = '0';
ALTER SYSTEM SET log_truncate_on_rotation = 'on';
ALTER SYSTEM SET log_parameter_max_length = '10kB';
ALTER SYSTEM SET shared_buffers = '16GB';
ALTER SYSTEM SET maintenance_work_mem = '500MB';
ALTER SYSTEM SET work_mem = '16MB';
ALTER SYSTEM SET autovacuum_vacuum_cost_limit = '2000';
ALTER SYSTEM SET autovacuum_max_workers = '20';
ALTER SYSTEM SET huge_pages = 'try';

When using Proxy Pools:

Set the following values in pgbouncer.ini:

default_pool_size = 100
max_user_connections = 1800
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