Proxmox Backup Server vs Restow: an honest comparison

Proxmox Backup Server (PBS) is Proxmox's own backup system for Proxmox VE virtual machines, containers and Linux hosts. It is mature, free and open source. Restow is a self-hosted backup and archive for Microsoft 365, IMAP mail, servers and clients and, as a preview, Proxmox VE. The two overlap on Proxmox VE and hardly anywhere else.

By Lucas Flores, IT Systeme Flores UG. Last updated 2026-10-21

Proxmox Backup Server documentation (version 4.2.8-1, page dated 2 October 2026), the Proxmox VE documentation (9.2.13) and Proxmox's pricing page read on 2026-10-15.

The short answer

Choose Proxmox Backup Server if Proxmox VE is what you protect. It is the backup system Proxmox builds for its own platform and has been stable since 2020. It is free and open source (AGPL v3), and it does things Restow does not do today: live restore and single-file restore from the Proxmox VE interface, tape, sync between servers and namespaces.

Choose Restow if Proxmox VE is only one of several things you protect and the rest is Microsoft 365, mail and servers: one tool, one restore check for every kind of backup, one archive and many isolated tenants. Restow's Proxmox VE support is a preview, for Proxmox VE 8.4 and newer, not yet recommended as your only backup, and the release notes say it has not yet run on a real Proxmox VE host. For Proxmox VE alone, PBS is the better choice.

At a glance

Aspect	Restow	Proxmox Backup Server
Price model	Community free. Business €595, Service Provider €1,950, one-time, net (pre-sale until release: €476 and €1,560). Pre-sale licenses include every 1.x update; from version 1.0, a license includes 12 months of updates, then an optional update year (Business €295, Service Provider €595 net per year). No per-user fee.	Free and open source (AGPL v3), with no limits on storage or clients. Subscriptions are per server and add the enterprise repository, which Proxmox recommends for production, and support. Proxmox lists EUR 1,120 to 4,480 per server and year for production support and EUR 560 for non-production use (read 2026-10-15).
What it protects	Microsoft 365 mail, calendar, contacts, OneDrive and SharePoint Online sites, IMAP mailboxes, imported mail files, Linux and macOS servers and clients (file-level agent), SMB and NFS file shares without an agent and, as a preview, Proxmox VE VMs and containers.	Proxmox VE virtual machines and containers, and Linux hosts through the proxmox-backup-client (file archives and block-device images). The documentation describes no Microsoft 365 or mailbox backup.
Where it runs and stores	Self-hosted: one Docker Compose stack on a Linux server or VM you control. Your choice: local disk, S3-compatible object storage or NFS, in the region you pick. Immutable backups (S3 Object Lock) can be switched on per repository.	Its own server, built on Debian, installed from an ISO or on top of Debian; Proxmox advises a separate physical server rather than the Proxmox VE host. Datastores on ext4, xfs or ZFS, removable datastores, or S3-compatible object storage with a local cache.
Deduplication, incremental, encryption	Content-defined chunks, deduplicated within a tenant and encrypted with AES-256-GCM, one key per tenant. Incremental through Microsoft Graph delta queries and, for Proxmox VE VMs, changed 4 MiB blocks.	Deduplication on the server, incremental backups that send only changed data, zstd compression, optional client-side AES-256-GCM encryption (not on by default) and TLS in transit.
Checking backups	A weekly sampled restore check reads data back through the restore path and compares it with the recorded hashes; Proxmox VE guests count in recovery readiness and, since 0.4.2, every new restore point of a guest is read back within minutes of its backup, and file shares are checked after every new restore point. A Proxmox VE job can also run a monthly restore check that restores one guest into a pool and deletes it again, and, as a preview and off by default, boot tests: a restore point is restored as a new guest cut off from the network, started, checked for an answer from the guest agent and deleted again.	Verify jobs check stored backups against their SHA-256 checksums on a schedule. The documentation recommends re-verifying at least monthly and testing restores to a new guest, and describes no built-in scheduled restore test.
Copies elsewhere	Copy repositories on other storage for mail, Microsoft 365 (SharePoint sites included), IMAP and Proxmox VE VM data. Servers, clients, file shares and Proxmox VE containers stay in the primary repository.	Sync jobs pull from or push to another Proxmox Backup Server, sending only new data; tape backup to LTO libraries, with WORM cartridges supported.
Restoring Proxmox VE guests	A whole guest comes back as a new guest with a new VMID, in the pool restow-restore. Files of a container and, as a preview, of a VM can be browsed in Restow and downloaded as a ZIP; they are not put back into a running guest. No live restore, no restore of privileged containers.	From the Proxmox VE interface, with live restore (the VM starts before the restore has finished) and single-file restore. Proxmox VE offers both only for backups on Proxmox Backup Server.
Source code, format and several customers	Apache 2.0 core, Business and Service Provider modules under the Restow license terms, open documented storage format with a standalone restore tool. Many isolated tenants, each with its own key, in the Service Provider edition.	AGPL v3 source, with file formats and the backup protocol documented. Namespaces and permissions separate users and backup sources inside a datastore.

Where Proxmox Backup Server is strong

Built by Proxmox for Proxmox VE: backup jobs, restore, live restore and single-file restore sit in the Proxmox VE interface.
Mature: in development since 2018 and stable since November 2020, free and open source (AGPL v3), with no limits on storage or clients.
Incremental, deduplicated backups with SHA-256 integrity checks, zstd compression and client-side AES-256-GCM encryption.
Verify jobs, prune jobs with a simulator, garbage collection and namespaces up to 8 levels deep.
Remote sync to another server and tape backup with LTO, including WORM cartridges.
A command-line client for file-level and image backups of Linux hosts.
Ransomware guidance in the documentation: a write-only token per host, sync that keeps snapshots that vanished at the source, off-site copies and regular restore tests.

Where Restow is different

One tool for Microsoft 365, IMAP mail, servers and clients and Proxmox VE, with one place that shows what is protected.
A sampled restore check for every kind of backup (weekly for mail, within minutes of each new backup for Proxmox VE guests, after each new backup for servers and clients), shown as recovery readiness: a backup that has not been read back shows as Unverified.
An append-only mail archive with a SHA-256 hash chain in every edition; capture from the mailboxes, journal receipt, enforced retention and legal hold, designed for GoBD-compliant use, in Business and Service Provider.
Optional boot tests of Proxmox VE restore points (a preview): the guest is restored as a new guest cut off from the network, started and deleted again; green means the guest agent answered.
Immutable backups per repository, off until an administrator turns them on (S3 Object Lock), and ransomware detection on every new restore point, a tripwire and not a virus scanner, with a retention hold while a finding is open.
Many isolated tenants, each with its own key, delegated administrators and a provider overview (Service Provider edition).
Agents for servers and clients that are append-only by design and never hold the credentials of the storage.
Restores are non-destructive by default, and users can restore their own mailbox.

When Proxmox Backup Server is the better choice

If Proxmox VE is what you protect, PBS is the better choice today. It is the backup system that Proxmox builds and documents for its own platform, it has been stable since 2020, and it offers what Restow does not: live restore and single-file restore from the Proxmox VE interface, tape, replication between servers and namespaces. Restow's Proxmox VE support is a preview with the limits listed below, and the release notes say it has not yet run on a real Proxmox VE host.

PBS is also the better choice if you want a vendor that sells support for the backup system of your hypervisor, or if you need to hand a Proxmox VE backup to a team that already knows the Proxmox tools.

When Restow fits, or fits alongside

Restow fits if Proxmox VE is one of several things you protect: Microsoft 365 mail, OneDrive and SharePoint sites, IMAP mailboxes, file shares, Linux and macOS servers and some Proxmox VE guests, for your own company or for customers. Then one tool, one recovery readiness view, one audit log and one tenant model can matter more than the Proxmox-specific extras, and a copy repository can place Proxmox VE VM data on another provider's storage. Restow also offers immutable backups per repository and ransomware detection; both pages state their limits.

Because the Proxmox VE part of Restow is a preview, run it next to what you have. PBS can stay the backup of your Proxmox VE hosts while Restow takes the rest; Restow does not replace it for that today.

How each one connects to Proxmox VE

Proxmox VE has had an interface for external backup providers since version 8.4 (April 2025). Restow uses it, through a storage plugin and a helper on each node, and it reads only changed 4 MiB blocks of a VM disk. PBS is integrated into Proxmox VE as a storage of type pbs, available since Proxmox VE 6.3. See Proxmox VE backup (preview) for what Restow does and does not do there.

On Restow's side, a backup job takes the cadences of a mail job since 0.4.2 (every few hours, daily, chosen weekdays, monthly or a cron expression, not more often than hourly), and a queued or running backup can be withdrawn or stopped from the web app, without SSH on the node; the run ends as cancelled, not as failed. Both are part of the preview and were tested against a simulated node.

What Restow does not do (yet)

Proxmox VE is a preview in every edition, for Proxmox VE 8.4 and newer, and not yet recommended as your only backup. The release notes say it was tested against qemu-nbd, qemu-img and restic and, for the node onboarding, against stand-ins for the node tools, but not on a Proxmox VE host. The 0.4.0 and 0.4.2 additions (progress display, boot tests, file restore of VMs and containers, stopping a backup, the restore check after every backup) were tested against the simulated node of the test suites, not on a Proxmox VE cluster.
A restore of a whole guest always creates a new guest. There is no live restore, no restore of privileged containers and no backup of VM templates. Files of a container and, as a preview, of a VM can be downloaded as a ZIP, not put back into a running guest; VM file restore reads GPT and MBR partitions and linear LVM volumes with ext2/3/4, XFS, NTFS and FAT, and not btrfs, ZFS, ReFS, LVM thin, RAID, BitLocker or LUKS. Nodes must be x86_64, and a cluster belongs to one tenant.
Restow has no tape backup and no replication between servers. A copy repository covers Proxmox VE VM data, not containers and not file shares.
Immutable backups are off until an administrator turns them on for a repository. S3 Object Lock (compliance or governance mode, 1 to 3650 days) was tested against a simulated S3 service only, not a real one; directories and NFS get only a deletion delay, which is not immutability; the installation's default repository cannot be made immutable.
Ransomware detection is a tripwire, not a virus scanner: a restore point without findings proves nothing, and the detection was tested with simulated attacks, not with live ransomware.
Restow does not back up Teams chats. It backs up SharePoint Online sites since 0.4.0, without attachments of list items, site design, navigation and workflows.
The automated Microsoft 365 backup and restore check against a real tenant is not active yet: check 4 of the release pipeline was skipped in every release so far; Microsoft 365 is covered by tests against a simulated Graph API.
Licenses include no support, setup, operation or SLA.
Restow is a beta: do not use it as your only backup.

Status of every feature: roadmap · pricing

Proxmox Backup Server: the facts, with sources

Each line is taken from Proxmox Backup Server's own documentation unless the rating says otherwise. "Checked: not found" means we looked in the named sources and did not find it, which is not proof that it does not exist.

Fact	Source	How solid
Proxmox Backup Server is a client-server backup system for virtual machines, containers and physical hosts, designed to work especially well with Proxmox VE, with a web-based management interface. It is free and open source under the AGPL v3, with no artificial limits on storage or client count.	PBS documentation, Introduction	Official source
Main features: deduplication, incremental backups (only changed data is read and sent), SHA-256 integrity checks, Zstandard compression, remote sync that transfers only new data, client-side AES-256-GCM encryption with TLS for all traffic, and tape backup. Development began in October 2018, the beta followed in July 2020 and the stable release in November 2020.	PBS documentation, Introduction	Official source
Datastores are directories in a standard Unix file system (ext4, xfs or ZFS) with retention settings and optional prune and garbage collection schedules; removable datastores are possible. S3-compatible object stores are documented as a backend, with a required local cache (64 to 128 GiB recommended); the documentation warns that providers may charge for storage, requests and egress.	PBS documentation, Backup Storage	Official source
Namespaces form a hierarchy of up to 8 levels that separates users or backup sources and avoids naming conflicts; permissions are set per namespace.	PBS documentation, Backup Storage	Official source
Retention uses keep-last, keep-hourly, keep-daily, keep-weekly, keep-monthly and keep-yearly in sequence, with a prune simulator. Pruning removes snapshot metadata; garbage collection frees the data in two phases later, and chunks younger than a cutoff of 24 hours and 5 minutes before the start are kept for the next run.	PBS documentation, Maintenance Tasks	Official source
Verify jobs check backup integrity on a schedule and can skip already verified snapshots or re-verify after a set period. The documentation recommends re-verifying all backups at least monthly to catch bit rot.	PBS documentation, Maintenance Tasks	Official source
Sync jobs pull (the default) or push between Proxmox Backup Server installations, with options such as remove-vanished, verified-only, encrypted-only, namespace mapping and rate limits.	PBS documentation, Managing Remotes and Sync	Official source
Ransomware guidance: existing backup blocks are never rewritten; use a separate token per host or cluster with only the Datastore.Backup privilege, which allows creating backups but not deleting or changing them; prune on the server with prune jobs; configure sync jobs not to delete snapshots that vanished at the source; keep off-site copies through sync and tape; test restores to a new guest. Verification jobs are described as a supplementary measure that an attack might evade.	PBS documentation, Backup Storage, Ransomware Protection and Recovery	Official source
Tape backup supports LTO-5 and newer (best effort for LTO-4), tape libraries through the SCSI Medium Changer protocol, media pools, hardware encryption on LTO-4 and newer, and WORM cartridges with a keep retention policy. The documentation says restores from tape are much slower than from disk, because tapes offer no random access.	PBS documentation, Tape Backup	Official source
The proxmox-backup-client command-line tool creates and restores file-level backups (pxar archives) and images of block devices, with change-detection modes that can skip unchanged files. Client-side AES-256-GCM encryption uses a key you create; losing it makes the backups unreadable. A snapshot can be marked protected, which blocks deletion.	PBS documentation, Backup Client Usage	Official source
The client documentation names Linux only; no Windows or macOS client was found in the official documentation.	PBS documentation, Backup Client Usage, FAQ	Checked: not found
No backup of Microsoft 365, Exchange Online or IMAP mailboxes is described in the introduction, the storage chapter or the client chapter.	PBS documentation, Introduction, Backup Client Usage	Checked: not found
No built-in scheduled restore test is described: the documentation recommends regular test restores to a new guest, automated where possible, next to the verify jobs.	PBS documentation, Backup Storage, Maintenance Tasks	Checked: not found
A Proxmox Backup Server is added to Proxmox VE as a storage of type pbs, available since Proxmox VE 6.3; backup jobs and restores run from Proxmox VE.	PBS documentation, Proxmox VE Integration	Official source
Live restore (a VM starts before its restore has finished) and single-file restore in the Proxmox VE interface are available only for backups on Proxmox Backup Server. Protected backups are excluded from pruning.	Proxmox VE documentation 9.2.13, Backup and Restore	Official source
Recommended server: a 64-bit CPU with at least four cores, 4 GiB of RAM plus about 1 GiB per TiB of backup storage, fast local storage with enterprise SSDs preferred, and a separate physical server rather than the Proxmox VE host so that backups survive a hypervisor failure.	PBS documentation, Installation	Official source
The Enterprise repository needs a subscription key and is the one recommended for production. The No-Subscription repository needs no key and is meant for testing or non-production use, with less tested packages.	PBS documentation, Installation	Official source
Subscriptions are priced per server and year: Premium EUR 4,480, Standard EUR 2,240, Basic EUR 1,120, and a Community plan at EUR 560 described as for non-production use. Every plan includes all features, unlimited backup storage and unlimited backup clients; the plans differ in support.	Proxmox: Proxmox Backup Server pricing	Official source
Proxmox VE 8.4, released on 9 April 2025, added an interface that lets external backup vendors write plugins that handle backup and restore inside the Proxmox VE backup stack and web interface.	Proxmox: Proxmox Virtual Environment 8.4 available	Official source

Frequently asked

Is Proxmox Backup Server free?

The software is free and open source under the AGPL v3, and the documentation says there are no artificial limits on storage or clients. Subscriptions are sold per server: they add access to the enterprise repository, which Proxmox recommends for production servers, and technical support. Proxmox publishes the plans and prices on its pricing page.

Can Restow replace Proxmox Backup Server?

For Proxmox VE alone, not today. Restow's Proxmox VE support is a preview with no live restore and no tape, files of a VM can only be downloaded (also a preview), not put back into the running guest, and the release notes say it has not yet run on a real Proxmox VE host. It can sit beside PBS if you also protect Microsoft 365, mail and servers.

Does Proxmox Backup Server back up Microsoft 365?

Its documentation describes backups of virtual machines, containers and physical hosts, and it does not describe Microsoft 365 or mailbox backup. Restow backs up Exchange Online mail, calendar, contacts, OneDrive and SharePoint Online sites, and IMAP mailboxes.

Do Restow and Proxmox Backup Server back up VMs the same way?

Both plug into the backup stack of Proxmox VE and send only changed data. PBS uses the client built into Proxmox VE. Restow uses the interface for external backup providers that came with Proxmox VE 8.4 and stores the data in its own encrypted chunk store, in a repository you choose.