OpenZFS vs Btrfs: Copy-on-Write Filesystems for Linux Compared
Choose OpenZFS for a storage appliance or server where mature pool management, replication workflows, and cross-platform operational experience justify an out-of-tree Linux module. Choose Btrfs for tight Linux integration, lightweight snapshots, and flexible single-host filesystems. Neither eliminates backups, and neither should be selected without testing the exact disk topology and failure procedure.
The integration and administration models differ
OpenZFS manages disks in pools and vdevs, then exposes datasets and zvols with checksums, snapshots, compression, quotas, and send/receive. On Linux it is distributed separately from the upstream kernel, which affects installation and kernel-upgrade testing. The OpenZFS FAQ explains the project and platform support.
Btrfs is part of the Linux kernel and combines a filesystem with multi-device management, subvolumes, snapshots, checksums, compression, and send/receive. Integration does not make every feature equally mature. The official Btrfs status page identifies feature-specific maturity and should be checked against the deployed kernel and userspace tools.
Redundancy and caching claims need precision
A ZFS vdev's redundancy layout constrains how capacity can be expanded; design replacement and expansion before creating the pool. Btrfs can add and remove devices and rebalance data, but parity RAID profiles have historically carried important caveats. For either system, model simultaneous failures, an unreadable sector during rebuild, and replacement with a slightly smaller drive.
ZFS L2ARC is a secondary read cache and a separate SLOG stores the synchronous-write intent log; neither is a generic speed device, and a SLOG does not cache ordinary asynchronous writes. Btrfs has no native equivalent called an “SSD tier.” Layering a block cache underneath a checksumming copy-on-write filesystem changes failure behavior and must be validated rather than described as a built-in Btrfs feature.
Hardware behavior limits data-integrity promises
Checksums detect corruption, but repair requires another valid copy. Drives, USB bridges, controllers, and virtualized storage can also lie about completed flushes or discard commands. The Btrfs hardware guidance documents these lower-layer risks. Use error-correcting memory where the risk warrants it, monitor device errors, schedule scrubs, and replace failing media promptly.
Build the candidate pool with representative data, then test snapshots, quota pressure, disk replacement, scrub findings, an interrupted write, replication, and bare-metal restore. Keep at least one backup on a different system and verify restoration. OpenZFS's getting-started documentation and the Btrfs manual describe mechanisms; only a recovery drill proves the organisation can operate them.
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