Synology 가상 머신 클러스터의 운영 환경: 3노드 VMM Pro 구성

A Synology virtual machine cluster is not just a lab toy. This store, our mail relay, our sister brand and several hosted websites all run as guests on three Synology NAS units joined in one Virtual Machine Manager cluster, protected by a VMM Pro license. Eight guests live on it today, seven of them running around the clock, and six are replicated on a schedule to a standby host that spends most of its life asleep. This article walks through that Synology virtual machine setup as it actually runs: which hardware does what, why we chose scheduled replication over high availability, how we would fail over, and the limits you should know before copying it.

SynoPower Club 포인트: The question I get most from customers buying VMM Pro is what it looks like when a real business depends on it. So here is ours, warts included. The console shows a permanent warning because one host is switched off on purpose, the standby only wakes up to collect replicas, and the web server inside the store guest has a note taped to it for failover day. None of that is in the brochure. All of it is why a Synology virtual machine cluster costs us a fraction of what the same redundancy would in a rented data centre.

What a Synology Virtual Machine Cluster Looks Like in Production #

Virtual Machine Manager lets up to seven Synology NAS hosts share one console. Each host keeps its own storage and runs its own guests, and the free edition already manages them as a cluster. What VMM Pro adds is the ability to act across hosts: move a running Synology virtual machine from one box to another, restart it elsewhere automatically, or copy its snapshots to another host on a schedule.

That distinction shapes everything below. Our cluster is three hosts, but the value comes from the protection plans that run between them, not from the fact that they appear in one list. If you are still deciding between editions, our comparison of Virtual Machine Manager and VMM Pro covers the full feature split.

Our Three Synology Virtual Machine Hosts and What Runs Where #

The cluster mixes three generations of Synology hardware, and each Synology virtual machine host is given the job that suits it.

Host	Role	What it runs
DS1621xs+	Primary production host	This store as a Virtual DSM guest on NVMe storage, plus one customer website
FS1018	Secondary production host	Our mail relay, our sister brand website, two hosted websites and one small guest
FS2017	Cold standby and replica target	Nothing live; it receives scheduled replicas and powers down again

The store sits on the DS1621xs+ because it is the busiest Synology virtual machine in the cluster and has the history to prove it. We moved it there from the FS1018 in August 2026 after measuring that the smaller host was running ten virtual CPUs on four hardware threads. Both production hosts use the same generation of processor at the same clock speed, so a single request runs at the same speed on either. What the bigger host buys is room: more threads, so busy guests stop competing for the same cores.

Why We Chose Replication Over High Availability #

On paper, three hosts is exactly what VMM Pro high availability needs. Synology requires at least three hosts in the cluster, and they decide cluster health by majority, which is why the white paper recommends an uneven number of nodes.

The catch is that high availability expects those hosts to be online. Our third host is a cold standby that is switched off most of the time to save power and noise, so the cluster could not keep the majority that automatic failover depends on. Rather than run a third machine all day, we chose protection plans: scheduled snapshots with remote replication to the standby. Failover becomes a deliberate, manual step measured in minutes, not an automatic one measured in seconds.

For a small shop that trade is worth making. The standby costs almost nothing to run, and the replicas are already sitting on it when we need them. If uptime ever mattered more than the power bill, turning the standby into an always-on third host would unlock high availability on the same license.

Replicating a Synology Virtual Machine to a Standby Host in 4 Steps #

This is the sequence we followed to protect each guest. It needs VMM Pro, at least two hosts in the cluster, and Btrfs volumes on both the source and the destination.

How the Protection Plans Are Tuned #

Six of our eight guests have a protection plan, and every protected Synology virtual machine replicates to the standby. Not every guest deserves the same schedule, so they fall into two groups.

• Every twelve hours: this store, the mail relay and one customer website, where losing a day of changes would hurt.
• Once a day at 04:00: two hosted websites and the small guest, where daily is enough.

Retention follows the same logic, using the built-in policies Virtual Machine Manager names by recovery point objective: the busiest guests keep the hourly policy, quieter ones the daily or weekly policy. The two guests without a plan are a retired project tracker that is powered off and one website that does not have a plan yet.

One detail caught us out early. The free edition keeps at most 32 snapshots per guest, and a twelve-hour schedule reaches that in sixteen days. VMM Pro raises the ceiling to 255, but we still lock any manual snapshot we want to keep, so the schedule never rotates it away.

How a Small Team Protects Every Synology Virtual Machine #

The whole cluster is run by a very small team, which is the point. No one watches dashboards all day, so the design has to protect every Synology virtual machine without anyone remembering to press a button.

Protection plans run on their own schedule. The standby wakes, receives replicas and sleeps again. Before any risky change, such as resizing a guest or updating plugins, we take a locked snapshot first; our right-sizing walkthrough shows that routine in practice. When something did go wrong on the store, as in the contact form email bombing we traced this month, the logs, the mail and the snapshots were all on hardware we control.

What Failover Day Looks Like #

A replica carries everything inside the Synology virtual machine, including settings that were tuned for the host it came from. That is the part people forget.

The store guest is tuned for the DS1621xs+, including how many simultaneous workers its web server is allowed to start. If the store ever has to run on a host with fewer hardware threads, that limit has to come down before traffic arrives, or the guest will overload itself. Our runbook lists that change as the first step after powering on a replica, followed by checking that the site, checkout and mail all answer.

Write your own list before you need it. Replication gets the Synology virtual machine to the other host; a checklist gets it working there.

Capacity Planning: Memory Is the Real Limit #

On our hosts every running guest’s memory is reserved and locked, so it cannot be shared or reclaimed by DSM. That makes memory, not CPU, the true capacity limit of a Synology virtual machine cluster.

A standby or secondary Synology virtual machine host is only useful if it has enough free memory to take the guests that might land on it. That is why we cut the store guest from sixteen gigabytes to eight once measurements showed it never needed more. The eight gigabytes we got back is headroom another host can use during a failover, without buying anything.

Why This Cluster Runs on Synology and VMM Pro #

The honest reason is cost against effort. Three Synology NAS units that also store our files, one VMM Pro 라이센스 and the free Virtual DSM instance each host includes give us replicated, snapshot-protected hosting managed from a single console. Every guest can be rolled back in minutes and rebuilt on another box from a replica.

It also keeps us honest as a reseller. The licenses we sell run our own business, so when a customer asks whether VMM Pro works in production, the answer is on the page you are reading.

Synology Virtual Machine Cluster Limits and Caveats #

A replicated Synology virtual machine is only as fresh as its schedule. The store replicates every twelve hours, so in the worst case a failover restores it as it was up to half a day earlier. That is the price of a sleeping standby, and the first setting we would tighten if order volume grew.

A cold standby also means the console always shows a warning about a host it cannot reach. That is the design working, not a fault, but it does mean real warnings are easier to miss. Check what the warning is about before dismissing it.

High availability is not backup. Neither is replication on its own: a mistake or malware inside a guest replicates too. Keep locked snapshots and an off-host copy you can go back to.

Finally, VMM only runs on compatible models with Btrfs volumes, and mixed hardware means mixed performance. Test a failover on the smallest host in your cluster, because that is where a guest will struggle first.

자주 묻는 질문 #

참고 자료 및 비디오 튜토리얼 #

• Protection in Virtual Machine Manager, covering protection plans, snapshots and remote replication.
• High Availability in Virtual Machine Manager, including the three-host requirement.
• Cluster management in Virtual Machine Manager, on adding and managing hosts.
• Synology VMM white paper, with quorum, network and cluster design guidance.
• VMM Pro License Pack, explaining 3-node and 7-node packs and license terms.

A walkthrough of Virtual Machine Manager and a guide to migrating guests on a Synology NAS. The third video covers Synology High Availability, a different product that mirrors a whole NAS to an identical passive twin, useful for seeing how it differs from VMM clusters.

Building your own cluster? Start with a VMM Pro 라이센스 for replication and live migration, add Virtual DSM 라이센스 for extra DSM guests, or browse every license on SynoPower Club.