XFS

Migration Guide: Moving from XFS to ZFS

XFS is a high-performance file system often used in enterprise environments for handling large-scale data storage and demanding workloads. However, ZFS provides additional advantages such as built-in RAID, end-to-end data integrity, snapshots, and more efficient data management capabilities. Migrating from XFS to ZFS allows administrators to leverage these advanced features while maintaining storage performance and reliability.

This guide explains the steps required to migrate data from an XFS file system to ZFS, including pool creation, data migration, and post-migration configurations.

Why Migrate from XFS to ZFS?

While XFS offers excellent scalability and performance, ZFS provides a broader range of features that may be beneficial for enterprises or users looking for better storage management, including:

• Data Integrity: ZFS uses end-to-end checksumming for every block of data, ensuring early detection of data corruption and automatic repair using redundancy.
• Snapshots: ZFS supports native snapshots, which allow for quick backups and recovery of point-in-time data states, something XFS lacks natively.
• Built-in RAID: ZFS includes integrated RAID support, eliminating the need for hardware RAID or external RAID software. RAID-Z1, Z2, and Z3 offer multiple levels of redundancy to guard against disk failures.
• Compression and Deduplication: ZFS provides efficient built-in compression and deduplication, which reduces disk usage and optimizes storage performance.

Prerequisites

Before starting the migration from XFS to ZFS, ensure the following steps have been taken:

• Backup critical data: Always back up data from the existing XFS file system before proceeding with the migration process.
• Install ZFS utilities: Depending on the operating system, install the required ZFS packages.

For example, on Debian-based systems, the following command installs the necessary utilities:

sudo apt install zfsutils-linux

For RHEL-based systems, the equivalent command is:

sudo yum install zfs

Step 1: Preparing a New ZFS Pool

1. Identify the Available Disks: Use the lsblk command to list available disks or partitions that will be used for the new ZFS pool:

   lsblk
   

2. Create the ZFS Pool: Based on the disk configuration, create a ZFS pool. For a single disk, the following command initializes the pool:

   sudo zpool create mypool /dev/sdb
   

For redundancy using a mirrored setup, the command is:

sudo zpool create mypool mirror /dev/sdb /dev/sdc

For RAID-Z configurations (RAID-Z1 for single parity), the command is:

sudo zpool create mypool raidz /dev/sdb /dev/sdc /dev/sdd

The new ZFS pool will be automatically mounted under /mypool by default.

Step 2: Migrating Data from XFS to ZFS

1. Mount the XFS File System: If the XFS file system is not already mounted, mount it using the following command:

   sudo mount /dev/sda1 /mnt/xfs
   

2. Transfer Data: Use rsync to copy data from the XFS file system to the newly created ZFS pool. This method ensures that file attributes, permissions, and hard links are preserved:

   sudo rsync -aHAXv /mnt/xfs/ /mypool/
   

Here, /mnt/xfs/ is the source XFS file system, and /mypool/ is the destination ZFS pool.

Step 3: Configuring the ZFS Pool

After migrating the data, configure the ZFS pool to optimize its features for the intended use case:

1. Enable Compression: Enable ZFS compression to reduce disk space usage. The lz4 algorithm is often the preferred compression method due to its balance of speed and compression efficiency:

sudo zfs set compression=lz4 mypool

2. Enable Deduplication (Optional): Deduplication helps reduce disk usage in environments where there are many redundant data blocks. However, it is resource-intensive and may not be suitable for all workloads:

sudo zfs set dedup=on mypool

Step 4: Monitoring and Verifying the ZFS Pool

1. Check Pool Status: Verify that the ZFS pool is functioning correctly by using the zpool status command. This command provides details about the health of the pool, any errors, and the overall status of the storage devices:

   sudo zpool status mypool
   

2. Perform a Scrub: Running a scrub checks for data integrity issues and repairs any inconsistencies using the pool's redundancy. It is a good practice to perform a scrub after migrating data:

   sudo zpool scrub mypool
   

3. Monitor I/O Performance: Use zpool iostat to monitor I/O performance, helping to identify any bottlenecks or underperforming disks:

   sudo zpool iostat mypool 5
   

Step 5: Post-Migration Cleanup

Once the ZFS pool is confirmed to be functioning correctly and the data migration is complete, the old XFS file system can be unmounted:

sudo umount /mnt/xfs

If desired, the old XFS partitions can be removed or reformatted to reclaim disk space or for other uses. This can be done using fdisk or parted tools.

XFS to ZFS Command and Utility Mapping

This table maps common commands and utilities used in XFS to their equivalents in ZFS.