Longhorn vs XtreemFS

Longhorn is a free, open-source distributed block storage system for Kubernetes. It replicates storage across nodes and data centers to increase availability, with V1 replicated, V2 replicated and V2 sharded with erasure coding volume types. Teams can schedule recurring snapshots and backups to NFS or S3-compatible secondary storage, and create disaster recovery volumes for recovery in a second Kubernetes cluster. A GUI dashboard is included, and the management UI is described as free. The software stack can be upgraded without disrupting running storage volumes. Installation options include kubectl, Helm, Fleet, Flux and ArgoCD. Longhorn supports mTLS for securing and encrypting gRPC communication between its control and data planes, but mTLS is disabled by default. Components need root access with privileged permissions for volume operations and management. Backups require an NFSv4 client, while ReadWriteMany volumes require NFSv4.1. Longhorn runs on Linux and supports API, web and self-hosted use. It is a CNCF incubating project; SUSE Storage is described as a Longhorn-based distribution with additional support, security, lifecycle management and certified integrations.

XtreemFS is a free, fault-tolerant distributed file system for general-purpose storage, available for Linux, macOS, Windows and self-hosted deployments. Files are replicated across storage servers, with automatic failover to a backup replica if the primary fails. Full or partial read-only replicas support immutable files and can be used to create caches across datacenters. The project says an installation can grow to thousands of storage and metadata servers by adding or removing storage servers. POSIX compatibility makes it usable as an NFS replacement. SSL and X.509 certificate support are built in, and the site says XtreemFS can run over the internet without a VPN. A Hadoop client supports use as an HDFS replacement. Listed uses include filer replacement, HPC and Hadoop clusters, VM block storage and cross-branch sharing. Linux distribution packages and precompiled Windows and Mac OS X clients are available. The FAQ says a single volume may hold up to tens of millions of files, with no known limits stated for volumes and services. The project is open source under a BSD license and is developed by Zuse Institute Berlin.