PostgreSQL vs. MySQL: The Architect's Dilemma in 2012

It is 3:00 AM. Your pager is buzzing because the replication lag on the master database just hit 400 seconds, and the checkout page on your client’s Magento store is timing out. If you are running a high-traffic site in Norway, you know this nightmare. The choice between MySQL and PostgreSQL is rarely just about syntax; it is about sleep preservation, data integrity, and raw I/O performance.

For years, the LAMP stack (Linux, Apache, MySQL, PHP) has been the default standard for web development. But with the recent Oracle acquisition of Sun Microsystems, uncertainty is rippling through the open-source community. Meanwhile, PostgreSQL has quietly evolved from an academic curiosity into a performance beast with the release of version 9.1. At CoolVDS, we host thousands of database instances, and we see exactly where each engine breaks—and where they fly.

The Speed Demon: MySQL 5.5

MySQL is the engine of the web. It powers Facebook, Wikipedia, and likely your WordPress blog. With the release of MySQL 5.5, InnoDB finally became the default storage engine, replacing the archaic MyISAM. This was a critical shift. MyISAM relied on table-level locking, which meant if one user was writing to a table, nobody else could read from it. On a busy site, that queue builds up fast.

InnoDB brings row-level locking and ACID compliance (Atomicity, Consistency, Isolation, Durability) to the table. However, out of the box, MySQL is often configured for a server with 512MB of RAM from 2005. To get real performance on a modern CoolVDS KVM slice, you need to tune the buffer pool.

Optimizing my.cnf for Write Throughput

If you have a 4GB RAM VPS dedicated to MySQL, do not leave the defaults alone. Here is a battle-tested configuration snippet for /etc/my.cnf regarding InnoDB:

[mysqld]
# Allocate 70-80% of RAM to the buffer pool on a dedicated DB server
innodb_buffer_pool_size = 3G

# Separate buffer pool instances to reduce mutex contention (MySQL 5.5+ feature)
innodb_buffer_pool_instances = 4

# 1 = safest (ACID), 2 = faster but risky on crash, 0 = fastest but risky
innodb_flush_log_at_trx_commit = 1

# Method for flushing data to disk. O_DIRECT avoids double buffering with OS cache
innodb_flush_method = O_DIRECT

# Log file size. Larger logs mean fewer checkpoints but longer recovery time
innodb_log_file_size = 256M

Pro Tip: If you are migrating from MyISAM to InnoDB, remember that InnoDB is much hungrier for disk space and RAM. It creates a clustered index for every table. If your storage subsystem is slow, your database crawls. This is why we prioritize high-speed SSD storage on our hosting nodes. Rotational latency is the enemy of transactional databases.

The Fortress of Integrity: PostgreSQL 9.1

While MySQL focuses on read speed and web ubiquity, PostgreSQL (or "Postgres") focuses on being right. It is strictly SQL standards-compliant and offers features that developers drool over: transactional DDL, Window Functions, and with 9.1, synchronous replication.

We recently migrated a geospatial logistics client in Oslo from MySQL to Postgres. Why? PostGIS. The spatial capabilities in PostGIS far outstrip MySQL’s spatial extensions. Furthermore, Postgres handles complex joins significantly better due to its sophisticated query planner.

Tuning postgresql.conf for Heavy Lifting

Postgres handles memory differently. It relies heavily on the operating system's file system cache. Therefore, you do not allocate 80% of RAM to its internal buffer like you do with MySQL.

# /etc/postgresql/9.1/main/postgresql.conf

# Usually 25% of system RAM is a good starting point
shared_buffers = 1G

# Estimate of how much memory is available for disk caching by the OS
effective_cache_size = 3G

# Amount of memory for internal sort operations and hash tables before writing to disk
work_mem = 32MB

# Write Ahead Log (WAL) checkpoints. Increasing this reduces I/O spikes.
checkpoint_segments = 32
checkpoint_completion_target = 0.9

The Vacuum Problem: In older versions, table bloat was a massive issue requiring manual maintenance. The Autovacuum daemon in 9.1 is much improved, but on high-write systems, you still need to watch it closely. If Autovacuum lags, your disk usage will explode, and performance will tank.

The Infrastructure Factor: KVM vs. Noisy Neighbors

The best database configuration in the world cannot fix a choked hypervisor. In the budget hosting market, many providers use OpenVZ (container-based virtualization). In an OpenVZ environment, the kernel is shared. If your neighbor decides to compile a kernel or gets hit by a DDoS attack, your database latency spikes because the CPU scheduler is overwhelmed.

This is why serious architects choose KVM (Kernel-based Virtual Machine). At CoolVDS, our instances use KVM to ensure strict resource isolation. When you run `top` inside your server, the memory and CPU you see are yours.

Benchmarking Disk I/O

Before deploying your database, you should verify the disk performance of your VPS. In 2012, if you aren't getting decent IOPS, your database will lock up during backups. You can use a simple dd test or the newer ioping tool if available in your repo.

# A quick and dirty write test (don't run this on a production DB drive while active!)
dd if=/dev/zero of=testfile bs=1G count=1 oflag=direct

# Expected result on CoolVDS Enterprise SSD tier:
# 1073741824 bytes (1.1 GB) copied, 4.2 s, 255 MB/s

If you see speeds below 40 MB/s, you are likely on a legacy SATA drive overloaded with other customers. Move your data immediately.

Legal Compliance: Data in Norway

For our Norwegian clients, physical location matters. The Personopplysningsloven (Personal Data Act) and the strict guidelines from Datatilsynet mean that storing sensitive user data outside the EEA—or even outside Norway—can invite scrutiny. Latency is another factor. The round-trip time (RTT) from Oslo to a server in Frankfurt is decent (~25ms), but the RTT to a local CoolVDS node in Oslo is under 5ms. For a chatty application making hundreds of SQL queries per page load, that 20ms difference adds up to seconds of total load time.

Comparison: Which one to choose?

Conclusion

If you are building a standard Magento store or a WordPress network, MySQL 5.5 (or the emerging MariaDB fork) remains the pragmatic choice due to the massive ecosystem of tools and plugins optimized for it. However, if you are designing a custom application requiring complex transactions, strict foreign key constraints, or geospatial data, PostgreSQL 9.1 is the superior technical solution.

Regardless of your choice, the database is only as fast as the disk it sits on. Don't let IOPS bottlenecks kill your project.

Ready to test your replication setup? Deploy a high-performance KVM VPS with CoolVDS today and experience the stability of local Norwegian hosting.