Caelum is the intelligent file server published by GaLiLo, a modern storage gateway for businesses. In plain terms: Caelum presents itself to your users as a classic file server (Windows SMB and NFS shares), but adds on top of it automatic, transparent archiving to object storage (S3), snapshots, replication to a second site and high availability.
The goal: keep your hot data accessible locally at full speed, push your cold data to far cheaper object storage, all without your users having to change their habits and without ever having to manually re-download an archived file.
Caelum is not a "sovereign cloud" nor a storage provider. It is a gateway to the object storage that you choose (AWS S3, MinIO, Wasabi, Backblaze, Ceph, an S3 hosted in France, etc.). Your data stays yours, on the storage you decide.
Who Caelum is for#
Caelum targets organizations that operate one or more file servers (Windows NAS, Synology, QNAP, legacy filers) and want to:
- Reduce the cost of storing data that is no longer used day to day (archives, closed projects, old versions) by moving it to object storage, while keeping it accessible on demand.
- Modernize without disruption: keep SMB/NFS shares, Active Directory integration and user habits.
- Migrate an old NAS to a current platform (content audit, copy, cutover).
- Secure business continuity with snapshots, replication to a remote site and an optional high-availability setup.
This is typically the tool of a system/IT administrator or an MSP (managed service provider) who manages the file storage of an SMB or mid-market company.
Key concepts (Caelum vocabulary)#
Five notions come up everywhere in the interface. Understanding them is enough to get started with the appliance.
The storage pool#
The pool is the physical disk space managed by the appliance (ZFS engine, renowned for its robustness and snapshots). It is built at installation from one or more disks, with a topology of your choice: single disk, mirror (survives the failure of one disk) or RAID-Z (parity). Everything else — volumes, shares — sits on top of this pool.
Caelum manages a primary pool (galilopool, mounted under /galilo/data)
and, if needed, additional pools to consolidate or extend storage (each pool
carries a Primary or Additional role in the Storage pools view). A pool's
disks can be local disks or LUNs from an iSCSI array (SAN) attached from
the interface (see iSCSI targets).
The volume#
A volume is a logical container inside the pool. It carries the settings
common to everything it contains: quota (maximum size), snapshot policy,
default cloud destination and enabling of Windows "Previous Versions". You
generally create one volume per team or per project (e.g. accounting,
project-X).
The share#
A share is what your users see and mount from their workstation: a network
folder served over SMB (Windows: \\caelum\my-share) and/or NFS
(Linux/Unix). A share always belongs to a volume. There you set the protocols
served, an optional read-only flag, and the allowed access (by Active
Directory groups/users for SMB, by IP address for NFS).
The cloud destination (S3 target)#
A cloud destination is an object-storage vault, S3-compatible, that you declare in the appliance (endpoint, credentials, bucket, region) from the Cloud destinations view. It is the archiving destination. Caelum imposes no provider: you point to the S3 of your choice (AWS S3, MinIO, Wasabi, Backblaze B2, Ceph, a European sovereign S3…).
Tiering (archiving) and recall#
Tiering (also called archiving, or HSM for Hierarchical Storage Management) is the automatic movement of cold files (rarely accessed) from the local pool to the S3 target. Locally, the file is replaced by a stub: a lightweight marker that takes almost zero disk space but stays visible and clickable like the original file.
Recall is the reverse operation, automatic and transparent: as soon as a user opens an archived file, Caelum re-downloads it from S3 on the fly. The user simply sees the file open (with a short delay while it downloads) — they have nothing to do, no tool to launch.
From a Windows user's point of view, an archived file appears with the "offline" attribute (a small icon). It opens normally; Caelum handles the recall in the background.
The snapshot#
A snapshot is a point-in-time picture of a volume's state at a given moment, taken in a few seconds and occupying only the space of later changes. Snapshots let you roll back after a deletion or corruption, and can be exposed to Windows users as "Previous Versions". On the Caelum side, a single checkbox on a volume or a share ("Enable Previous Versions") is enough: the whole chain — SMB exposure and snapshot scheduling — is provisioned automatically. On the Windows workstation, the user right-clicks a file → Properties → Previous Versions.
How Caelum fits into your infrastructure#
- On the user side: nothing changes. They keep accessing SMB/NFS shares, with their usual Active Directory or LDAP accounts. The appliance shows up on its own in "Network" on Windows 10/11 and in the macOS Finder (NAS icon), with no configuration: network discovery (WS-Discovery and mDNS/Bonjour) is active by default.
- On the hot-storage side: the appliance serves active files from its local disks, at full network speed.
- On the cold-storage side: older files are pushed to your S3 object storage and recalled on demand.
- On the continuity side: regular snapshots, replication to a second site,
and an optional two-node high-availability setup, following two modes
of your choice:
- Shared storage — a single pool on a multi-writer SAN/iSCSI array; the failover is transparent between the two nodes (requires a SAN and, in production, a fencing mechanism).
- Replication ("Option A") — each node keeps its own local pool, and an asynchronous ZFS replication keeps the second node as a mirror; the failover is manual and does not require a shared array.
The result: a reduced local footprint (you only store locally what is actually used), a controlled cost (cold data goes to economical object storage) and an unchanged experience for users.
What Caelum is not#
- Not a cloud provider: you bring your own S3 storage.
- Not a backup product in the classic sense: tiering moves data (with a reference copy in S3), it does not duplicate it the way backup software would. For resilience, Caelum relies on snapshots and replication. Keep your existing backup strategy if it answers obligations of its own.
- Not a system that asks your users to learn a new tool: access remains standard SMB/NFS.
Going further#
- Install an appliance: see the installation guide.
- Day-to-day administration: see the administration guide.
- Detailed tasks (volumes, shares, S3, snapshots, replication, AD, HA, updates): see the task guide.
- Having a problem?: see troubleshooting and FAQ.