# Plan TrueNAS Time Machine capacity and separate replica protection > The TrueNAS Time Machine guide recommends client-side backup-size limits and warns that a multi-user share does not automatically replicate backup data to another pool or off-site location. - Canonical URL: https://update.dsesecurity.com/updates/plan-truenas-time-machine-capacity-and-separate-replica-protection/ - Publisher: Detection Systems & Engineering (DSE Security) - Author: DSE Security Editorial Team - Published: 2026-10-29T19:49:35+00:00 - Modified: 2026-10-29T19:50:08+00:00 - Last reviewed by DSE: 2026-10-29 - Resource type: Guide - DSE priority: Advisory - Topics: Networks & Infrastructure - Reading time: 3 minutes ## What you need to know The TrueNAS Time Machine guide recommends client-side backup-size limits and warns that a multi-user share does not automatically replicate backup data to another pool or off-site location. ## Potentially affected TrueNAS 25.10 Time Machine SMB share planning and supported macOS client-side backup-size configuration. ## DSE recommendation Review client capacity limits and a separately configured replica or off-site protection requirement before accepting the backup design. ## Article Bottom line: Decide how much backup space a client may consume and where a second protected copy must exist. Keep a working Time Machine destination separate from the evidence for that additional copy. ## Source fact: what the authority says The [TrueNAS Time Machine guide](https://www.truenas.com/docs/scale/25.10/scaletutorials/shares/smb/setupbasictimemachinesmbshare/) says maintained macOS versions allow a maximum Time Machine backup size to be set through the macOS UI. It generally recommends managing that size on the client for flexibility rather than relying on the server-side limit. Its multi-user Time Machine configuration does not automatically replicate backup data to another pool or off-site location. The guide directs administrators who need that protection to configure a replication task for the dataset. ## What the source does not establish This article covers the guide’s capacity and separate-copy decisions, not a guaranteed recovery point or restore time. It does not resolve version-specific multiprotocol coexistence notices or establish that a particular Mac has completed a recoverable backup. ## Applicability questions - Which Macs and data owners will use the destination? - What client-side maximum and shared capacity budget are intended? - Is another-pool or off-site protection required, and who configures it? - What independent backup and restore evidence must the owner accept? ## DSE recommendation: controlled next steps The following steps are DSE recommendations based on the cited source. DSE recommends a client-capacity worksheet with the intended maximum for each proposed test Mac and the shared destination’s approved capacity envelope. Have the data owner choose the retention and space requirements rather than copying a convenient example value. Confirm the actual client version and available setting before the pilot. Put the second-copy requirement on a separate line in the backup design. Name its destination, owner and expected protection interval. Do not mark that line complete simply because the multi-user Time Machine share has been created or appears as an available destination on a client. For a proposed two-client case, identify a harmless backup set on each Mac and record each intended size limit. Review the separate replication configuration for the backing dataset through the applicable official workflow. Keep destination encryption, credential custody and off-site access decisions in their own supported recovery plan. Preserve the initial share and client configuration before changing capacity settings. Ask the recovery operator to identify where the ordinary client backup and any separately maintained copy would be found. Leave a missing replica owner or destination unresolved rather than describing the system as fully protected. ## Verification and evidence Proposed verification: inspect each selected client’s effective limit and perform an approved harmless backup. Record the client, chosen destination and observed completion separately. Compare the actual space observations with the worksheet without promising that a size limit determines a particular retention duration. Verify the separately configured dataset copy against its own schedule and destination evidence. Rehearse an authorized recovery of a harmless marker from the required backup path, including the second copy where the plan calls for it. Keep client backup completion, replication completion and demonstrated file recovery as three distinct observations. ## Official references - [TrueNAS — Adding a Basic Time Machine SMB Share](https://www.truenas.com/docs/scale/25.10/scaletutorials/shares/smb/setupbasictimemachinesmbshare/) — official product documentation; confirm the installed release and configuration. Source review completed October 29, 2026. Recheck the official documentation and deployment-specific applicability before a production change. ## Primary reference - Name: TrueNAS — Adding a Basic Time Machine SMB Share - Authority: www.truenas.com - URL: https://www.truenas.com/docs/scale/25.10/scaletutorials/shares/smb/setupbasictimemachinesmbshare/ - Source publication date: Not stated by the source ## Citation and use Preferred citation: “Plan TrueNAS Time Machine capacity and separate replica protection,” DSE Security, https://update.dsesecurity.com/updates/plan-truenas-time-machine-capacity-and-separate-replica-protection/ Publishing principles: https://update.dsesecurity.com/updates/dse-updates-editorial-methodology/ Usage and citation policy: https://update.dsesecurity.com/usage/ Copyright © 2026 Detection Systems & Engineering. All rights reserved.