NAS for Time Machine: How to Back Up Your Mac Properly
Apple Time Machine is one of the best backup tools - if the destination storage works. An external USB drive is fine for one Mac. With multiple Macs or laptops that are not always plugged in, NAS is the right answer. 2026 setup guide.
Short version
Time Machine over NAS works via SMB (AFP is deprecated). Storage need: 2-3x your Mac data, minimum. Synology, QNAP, TrueNAS and Unraid all offer dedicated Time Machine targets with quota management. Per-Mac setup takes 10-15 minutes.
How much storage Time Machine actually needs
Time Machine does not store one snapshot but an incremental history. Rule of thumb:
- Minimum 2x Mac storage: 1 TB Mac -> 2 TB Time Machine quota
- Recommended 3-4x: 1 TB Mac -> 3-4 TB quota for usable history
- For pros (large files, frequent changes): 5x+ quota
With 4 Macs at 1 TB each, Time Machine without quotas can quickly eat 12-15 TB. Per-Mac quota is mandatory or one laptop will hog everything.
Setup: Synology DSM 7
- DSM -> Control Panel -> File Services -> SMB -> Enable SMB plus advanced "Enable Bonjour Time Machine broadcast"
- Create a user per Mac: Control Panel -> User -> Create
- Create shared folder: Control Panel -> Shared Folder -> "TimeMachine"
- Quota: right-click folder -> Edit -> Advanced -> Time Machine folder size per user
- On Mac: System Settings -> Time Machine -> Select Backup Volume -> SMB share appears after Bonjour discovery
Setup: TrueNAS Scale
- Create dataset with quota
- Create SMB share on dataset, Purpose: "Multi-protocol shares" or "Time Machine compatible"
- On Mac: when picking Time Machine disk -> type SMB path
smb://truenas.local/timemachine
Setup: Unraid
Time Machine plugin from Community Apps. After install:
- Unraid Plugin -> Time Machine -> pick disk
- Set quota per user
- Mac auto-discoverable via Bonjour
What drive size for Time Machine volume
Single-Mac home:
- 1 Mac with 256 GB SSD: 1 TB volume is enough
- 1 Mac with 1 TB SSD: 4-6 TB volume
- 2-bay Synology as TM target: 2x 8 TB mirror = 8 TB usable (good for 2-3 Macs)
Multiple Macs (family/studio):
- 4 Macs at 4 TB quota each: 4-bay 16 TB SHR-1 = 24 TB usable (with headroom)
- RAID 5 or SHR-1 with per-user quotas pays off here
Common issues and fixes
"Backup volume could not be created": SMB version mismatch. macOS 11+ needs SMB3, older NAS firmware defaults to SMB2. Force NAS setting to SMB3.
Connection drops mid-backup: Mac power management. In Energy preferences enable "Wake for network access" and "Power Nap".
Backup gets slow over time: Time Machine snapshots accumulate as APFS snapshots. Full volume = poor performance. Do not undersize the quota.
"Backup verifying" hangs: First volume verification after restore takes hours. Patience.
Wake-on-demand does not work: NAS must offer Bonjour Wake-on-Demand. Synology supports it, others vary.
Performance tips
SSD cache on NAS: Makes Time Machine noticeably faster - workload is metadata-heavy.
2.5 GbE or faster network: First backup of a new Mac with 1 TB data takes ~4 hours over 1 GbE, ~1.5 hours over 2.5 GbE.
Wired connection for first backup: Ethernet cable or Thunderbolt adapter. WiFi is fine for daily incremental backups.
Backup strategy: NAS alone is not enough
Time Machine on NAS protects against a dead Mac. But not against NAS failure, fire, or theft. Recommendation: 3-2-1 rule
- 3 copies (Mac plus NAS-TimeMachine plus cloud/second NAS)
- 2 different media
- 1 off-site
More: Backup strategies guide.
Recommendation by setup
1 Mac, simple: 2-bay Synology DS224+ with 2x 8 TB mirror. ~$600 all-in.
2-3 Macs family: 4-bay Synology DS923+ with 4x 8 TB SHR-1. Per-user quota. ~$1100.
Studio/pros: 4-bay TrueNAS or Unraid with RAID-Z1, 4x 16 TB. 1 TB SSD cache. ~$1500.
Related articles
Further reading
NAS as Surveillance Storage: NVR Setup Done Right
How to Plan Your Plex Media Server Storage