When setting up ZFS storage on FreeBSD, administrators often face this fundamental question. Both approaches will technically work, but they have different implications for performance, maintenance, and future flexibility.

Using raw disks (/dev/da0, /dev/ada1, etc.) is the simplest method:

zpool create tank /dev/da0 /dev/da1

Advantages:

• ZFS has complete control over the entire disk
• No partition table overhead
• Simpler disk replacement procedures
• Better alignment for optimal performance

Creating partitions first using gpart:

gpart create -s gpt /dev/da0
gpart add -t freebsd-zfs -a 4k /dev/da0
zpool create tank /dev/da0p1 /dev/da1p1

When this makes sense:

• Need to share disk with other filesystems
• Want to reserve space for partitions
• Special alignment requirements
• Using disks larger than 2TB with legacy systems

Modern ZFS implementations (FreeBSD 12+) automatically handle 4K sector alignment, making the performance difference negligible in most cases. However, whole disks typically show:

• 0.5-2% better throughput in benchmarks
• More consistent latency under heavy load
• Better performance during resilvering

Whole disks make replacement simpler:

zpool replace tank /dev/da0 /dev/da2

With partitions, you must first prepare the new disk:

gpart create -s gpt /dev/da2
gpart add -t freebsd-zfs -a 4k /dev/da2
zpool replace tank /dev/da0p1 /dev/da2p1

For dedicated ZFS storage servers, whole disks are generally preferable. The exceptions would be:

• Boot pools (must be partitioned)
• Mixed-use systems needing other partitions
• Specialized storage configurations

If you must partition but want ZFS to use most of the disk:

gpart create -s gpt /dev/da0
gpart add -t freebsd-zfs -a 4k -s 3900G /dev/da0

This leaves room for metadata while giving ZFS the majority of a 4TB disk.

To see how your existing pools are configured:

zpool status -v
gpart show

Look for either whole disk devices (da0) or partition devices (da0p1) in the output.

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When setting up ZFS storage pools on FreeBSD systems, administrators face a critical architectural decision: whether to use entire raw disks or create partitioned devices. Both approaches have valid use cases, and the optimal choice depends on your specific requirements.

Using whole disks is the simplest method and recommended for most general use cases:

# Using whole disks example
zpool create tank ada0 ada1 ada2

Advantages include:

• Automatic 4K sector alignment
• Simplified management with no partitioning overhead
• Maximum available space utilization
• Better performance for certain workloads

Creating FreeBSD-ZFS partitions offers more flexibility for advanced configurations:

# Partitioning disks first
gpart create -s gpt ada0
gpart add -t freebsd-zfs -a 1m -l disk0 ada0

# Creating pool with partitions
zpool create tank gpt/disk0 gpt/disk1

Key benefits of partitioning:

• Ability to reserve space for other filesystems or swap
• Easier disk replacement procedures
• Support for mixed-usage disks (ZFS + other partitions)
• Consistent device naming across reboots

While the performance difference is typically minimal (1-3% in most benchmarks), there are scenarios where partitioning can introduce slight overhead:

# Benchmark command example (adjust count for your needs)
time dd if=/dev/zero of=/tank/testfile bs=1M count=10000

For maximum throughput applications like high-performance databases, raw disks might provide marginal advantages.

In production environments, consider these factors:

Scenario	Recommended Approach
Dedicated ZFS storage servers	Whole disks
General purpose servers	Partitions (for flexibility)
All-SSD configurations	Either (SSD alignment less critical)
Mixed HDD/SSD setups	Partitions (for consistent management)

Regardless of your choice, watch for these potential problems:

# Check alignment for partitioned disks
gpart show -l

# Verify pool health
zpool status -v

# Check for performance issues
zpool iostat -v 1