Database Backup Transfer Time Estimation

Database Backup Transfer Estimation

Database backups combine two operations: dumping data to a file and transferring that file. The transfer time depends on the compressed dump size and available bandwidth.

Typical Dump Sizes and Compression

Database Size (Raw)	Uncompressed Dump	gzip Compressed	zstd Compressed
10 GB	8-12 GB	2-4 GB	1.5-3 GB
100 GB	80-120 GB	20-40 GB	15-30 GB
1 TB	800 GB - 1.2 TB	200-400 GB	150-300 GB

Compression ratios vary dramatically based on data content:

• Text-heavy data (logs, documents): 5:1 to 10:1
• Mixed data (typical OLTP): 3:1 to 5:1
• Binary/blob data (images, files): 1.5:1 to 2:1
• Already compressed data: ~1:1 (no benefit)

PostgreSQL Backup Example

For a 100 GB PostgreSQL database:

# pg_dump with compression
pg_dump -Fc mydb > backup.dump
# Typical size: ~25 GB (4:1 compression)

# Transfer time at 1 Gbps:
# 25 GB * 8 = 200 Gb
# 200 Gb / 1 Gbps = 200 seconds = 3 min 20 sec

Parallel Dump and Transfer

Modern backup tools can pipe dump output directly to a remote destination:

pg_dump -Fc mydb | ssh remote "cat > backup.dump"

This avoids needing local storage for the dump but is limited by the slower of: dump speed, network speed, or remote write speed.

Backup Window Planning

For a nightly backup window of 4 hours:

Available time: 4 hours = 14,400 seconds
At 100 Mbps (70% eff): 70 Mbps effective
Max transfer: 70 * 14,400 / 8 = 126,000 MB = ~123 GB

If your compressed backup exceeds 123 GB, you need more bandwidth, a longer window, or incremental backup strategy.