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High-Speed PostgreSQL Replication on OVH with FastTransfer

François Pacull
François Pacull, ARPE.IO Developer
2025-09-27 · 4 min · Benchmark · FastTransfer

Introduction​

PostgreSQL-to-PostgreSQL replication at scale requires tools that can fully leverage modern cloud infrastructure and network capabilities. FastTransfer is a commercial data migration tool designed to maximize throughput through advanced parallelization. This post demonstrates FastTransfer's performance transferring 113GB of TPC-H data between OVH c3-256 instances over a 20 Gbit/s network.

Infrastructure Setup​

For our testing environment, we deployed PostgreSQL on two OVH c3-256 instances in the Paris datacenter. Here's what we're working with:

  • OVH Instances: c3-256 (256GB RAM, 128 vCores @2.3GHz, 400GB NVMe)
  • Network: 20 Gbit/s vrack, Paris datacenter (eu-west-par-c)
  • OS: Ubuntu 24
  • PostgreSQL: Version 16
  • Dataset: TPC-H SF100 lineitem table (~600M rows, ~113GB)

Architecture diagram.

PostgreSQL Configuration​

Optimized for bulk operations: 80GB shared_buffers, 128 parallel workers, minimal WAL logging. Target tables: UNLOGGED, no primary keys.

Target Database Disk Performance​

The target PostgreSQL instance uses the native 400GB NVMe instance disk (not block storage) for database storage. This provides excellent I/O performance crucial for high-speed data ingestion:

FIO Benchmark Command​

fio --name=seqwrite --filename=/tmp/fio-test --rw=write \
    --bs=1M --size=8G --direct=1 --numjobs=1 --runtime=30 --group_reporting

Results​

Sequential Write Performance (8GB test, 1MB blocks):
- Throughput: 1,260 MB/s (1.26 GB/s)
- IOPS: 1,259
- Average latency: 787 microseconds
- 95th percentile: 1.5ms
- 99th percentile: 2.3ms

The native NVMe storage delivers consistent low-latency writes with over 1.2 GB/s throughput, ensuring disk I/O is not a bottleneck for the PostgreSQL COPY operations even at peak network transfer rates.

Network Performance​

The private network connection between source and target instances was tested using iperf3 to verify bandwidth capacity:

iperf3 Benchmark Command​

# On target instance
iperf3 -s

# On source instance
iperf3 -c 10.10.0.50 -P 64 -t 30

Results​

Network Throughput Test (64 parallel streams, 30 seconds):
- Average throughput: 20.5 Gbit/s
- Total data transferred: 71.7 GB
- Consistent performance across all streams

The network delivers full line-rate performance, slightly exceeding the nominal 20 Gbit/s specification. With 64 parallel TCP streams, the network provides ample bandwidth for FastTransfer's parallel data transfer operations.

FastTransfer Command​

FastTransfer version: 0.13.12

./FastTransfer \
  --sourceconnectiontype "pgcopy" \
  --sourceconnectstring "Host=localhost;Port=5432;Database=tpch;Trust Server Certificate=True;Application Name=FastTransfer;Maximum Pool Size=150;Timeout=15;Command Timeout=10800;Username=fasttransfer;Password=******" \
  --sourceschema "tpch_100" --sourcetable "lineitem" \
  --targetconnectiontype "pgcopy" \
  --targetconnectstring "Host=10.10.0.50;Port=5432;Database=tpch;Trust Server Certificate=True;Application Name=FastTransfer;Maximum Pool Size=150;Timeout=15;Command Timeout=10800;Username=fasttransfer;Password=******" \
  --targetschema "tpch_100" --targettable "lineitem" \
  --loadmode "Truncate" --method "Ctid" --degree 128

Note the Maximum Pool Size=150 in the connection string, increased from the default 100 to support 128 parallel threads.

Performance Results​

Transfer Time​

Transfer Time.

Transfer time: 749s (single thread) → 70s (128 threads)

Throughput Scaling​

Throughput.

Throughput: 145 MB/s → 1,880 MB/s (75% of 20 Gbit/s link capacity)

Results Summary​

  • 113GB transferred in 70 seconds (degree=128)
  • 1.88 GB/s peak throughput achieved
  • 10.7x speedup with 128 parallel connections
  • Optimal range: 32-64 threads for best efficiency/performance balance

Conclusion​

FastTransfer achieves 1.88 GB/s throughput when transferring 113GB of data between PostgreSQL instances, utilizing 75% of the available 20 Gbit/s network capacity. The 10.7x speedup with 128 parallel connections demonstrates excellent scalability on OVH's high-end infrastructure. These results confirm that FastTransfer can effectively saturate modern cloud networking for PostgreSQL-to-PostgreSQL migrations.