HomeTechOps

NAS

NAS migration without data loss

A NAS migration is not just a copy job. It is a sequence: inventory, copy, verify, backup, then retire the old path.

Best for: People moving from external drives, cloud-only folders, or an older NAS.

Inventory before moving

  • List source folders, sizes, owners, and what cannot be replaced.
  • Identify which source is currently the best copy.
  • Do not erase old drives just because the first copy finished.

Copy and verify

  • Copy in batches that are easy to check.
  • Open a sample of important files from the NAS destination.
  • Check counts, sizes, and any copy errors before moving to the next batch.

Retire old storage slowly

  • Keep the old drive or old NAS untouched until the new NAS has a backup.
  • Run one restore check from the new backup path.
  • Only then decide what can be wiped or repurposed.
Operator snapshotEvidence first
First proof

List every source path, owner, size, and which copy is currently best.

Screen to open

robocopy <source> \\<nas>\<share> /E /COPY:DAT /DCOPY:DAT /R:2 /W:5 /LOG:<path> (macOS/Linux: rsync -av --log-file=<path> <source>/ /Volumes/<share>/)

Expected signal

The migration scope and best copy are known.

Stop boundary

Stop before formatting, wiping, deduplicating, or bulk renaming original sources.

Layer path

1NAS migration is inventory, best-copy protection, destination health, copy method, verification, backup, then retirement.
2The old drive/NAS/cloud folder remains part of the safety net until the new NAS data has an independent backup and restore proof.
3Wipe, format, deduplicate, bulk rename, and rebuild actions are stop points until verification is complete.
Runbook

Step-by-step runbook

Start here. Do each check in order, compare it to the expected result, and stop when the evidence explains the failure or the safe stop point applies.

1

Inventory sources and best copy

Check: Create a table of source path, owner, size, last modified, and whether it is the current best copy.

Expected result: The migration has a controlled scope.

If not: If you cannot identify the best copy, do not delete or deduplicate.

2

Prepare the destination

Check: Check NAS storage health, free space, shares, and non-admin migration permissions.

Expected result: Destination is healthy and writable.

If not: If storage warnings appear, fix them before copying.

3

Copy a small batch with logs

Check: Copy one folder group and save the copy log or job result.

Expected result: The batch completes with no unexplained errors.

If not: If errors appear, recopy that batch before continuing.

4

Verify the batch

Check: Compare counts/sizes and open samples from important file types on the NAS.

Expected result: Files are usable, not merely present.

If not: If samples fail, keep source untouched and fix copy method.

5

Back up before retiring old storage

Check: Run NAS backup and restore one migrated file from that backup.

Expected result: The new NAS data has its own recovery path.

If not: If backup/restore is not proven, do not wipe old drives.

Safe stop: Stop before formatting, wiping, deduplicating, or bulk renaming original sources.

Decision tree

Decision tree

If: A source drive clicks, disconnects, or asks to format.

Then: Source health risk is high.

Action: Stop migration writes and protect the source.

Safe stop: Stop before repair, format, or repeated copy attempts if the source is the best copy.

If: Destination NAS shows degraded storage or low space.

Then: The destination is not ready.

Action: Fix storage health/capacity before migration.

If: Copy logs show errors.

Then: The batch is not complete.

Action: Resolve errors and recopy only the affected batch.

If: Counts match but sample files fail.

Then: Integrity or app format is suspect.

Action: Do not wipe the source; investigate copy method.

If: New NAS has no backup yet.

Then: Retirement is not safe.

Action: Back up and restore-test the NAS before wiping old storage.

Evidence

Evidence table

SymptomEvidence to collectLikely layerNext action
Many sources to migrate.Inventory table with paths, sizes, owners, and best copy.Scope/source mappingCopy in documented batches.
Destination not ready.NAS storage health, free space, share permissions.Destination healthFix before copying.
Copy reports errors.Robocopy/log output or NAS file-copy job log.Transfer integrityRecopy failed batch and keep source.
Old drive ready to wipe.New NAS backup job plus restore sample.Retirement safetyWait until independent backup restores.
Reference

Commands and settings paths

Windows copy with log

robocopy <source> \\<nas>\<share> /E /COPY:DAT /DCOPY:DAT /R:2 /W:5 /LOG:<path> (macOS/Linux: rsync -av --log-file=<path> <source>/ /Volumes/<share>/)

Where: PowerShell or Command Prompt on a Windows PC, adjusted for the actual source and NAS share.

Expected: The log shows copied files and no unexplained failures.

Failure means: Copy errors mean the batch needs attention before source cleanup.

Safe next step: Keep the source untouched and rerun only the affected batch.

Destination health

NAS admin UI > Storage Manager/pool/volume/disk health/free space

Where: In the NAS admin UI before and after each major batch.

Expected: Storage stays healthy and free space remains adequate.

Failure means: Warnings during migration can endanger the only new copy.

Safe next step: Pause migration and protect sources.

Permission test

NAS admin UI > shared folders/users/groups + create/read/delete one harmless test file

Where: Using the intended non-admin migration account.

Expected: The account can write and read only the intended share.

Failure means: Wrong permissions can create partial copies or admin-dependent data.

Safe next step: Fix groups before copying real data.

Backup and restore proof

NAS backup app > latest job > restore one migrated file to a temporary folder

Where: After the new NAS backup completes.

Expected: A migrated file restores from the backup, not just from the NAS live share.

Failure means: No restore proof means old storage should not be wiped.

Safe next step: Keep old sources until restore works.

Hardware boundary

Hardware and platform boundary

Change only when

  • Buy more NAS storage or migration tools only after inventory, destination health, copy logs, verification, backup, and restore proof show a real need.

Evidence that matters

  • Usable capacity, storage health visibility, permissions, copy logging, snapshots, backup targets, and UPS protection matter.

Evidence that does not matter

  • Raw bays or faster network gear do not matter if the source is unverified or the NAS has no backup.

Avoid

  • Avoid wiping sources, formatting drives, or bulk cleanup until the new NAS copy and independent backup both restore.

Last reviewed

2026-05-07 · Reviewed by HomeTechOps. Reviewed for NAS migration sequencing across source inventory, best-copy protection, destination health, logged copy, verification, backup, and safe retirement.

Source-backed checks

HomeTechOps turns official docs and conservative safety rules into a shorter runbook. These links are the source trail for the page direction.

Synology: Backup and data protectionUsed for NAS-as-local-layer guidance, offsite backup, and restore drills.Synology: Hyper Backup technical specificationsUsed for backup-version, restore, integrity-check, destination, and Hyper Backup Explorer assumptions.Synology: DSM Storage Manager technical specificationsUsed for storage pool, volume, disk-health, file-system, and RAID/SHR operating assumptions.NIST: Ransomware guidanceUsed for conservative backup and recovery assumptions around independent copies, ransomware, and restore readiness.