Worth fixing
One disk is one copy
This box has one bay, so your photos live on a single disk. If it fails, they are gone. Asustor's own RAID chapter says a Single volume offers no data protection. Keep a backup on a USB disk, and a further copy somewhere other than your home. RAID is not a backup: it protects against one dead disk only, so a copy off the box is still needed.
What to do
- ADM: open External Backup and set up a scheduled backup to a USB disk.
- Keep one more copy away from the house (a relative's disk or a cloud bucket).
Sources
Worth fixing
One disk holds everything, and a bay is empty
Only one disk holds your data, and the second bay is empty. Fill it. Experts split on how to use two disks: as a mirror, or as two separate disks where one backs up the other. For a family archive KEEP recommends the second. RAID is not a backup: it protects against one dead disk only, so a copy off the box is still needed.
Experts differ: the options
- Mirror the two disks (RAID1)
For: The box keeps running when one disk dies and nobody has to do anything. ADM offers RAID1 for two drives.
Against: A mirror copies a deletion, an overwrite, ransomware or file-system damage to both disks at once, and both disks sit in the same box.
- Two separate volumes, one scheduled to back up the other Recommended
For: The scheduled copy runs behind, so a deletion or an encryption is not copied until the next run; snapshots on the backup volume keep older history.
Against: If the main disk dies you must restore, and changes since the last run are lost. Keep snapshots on both volumes.
What to do
- Buy a second disk of the same size or larger, from a NAS-rated line.
- Decide between the two layouts below before you set it up; ADM can migrate a Single volume to RAID1 later, but cannot go back down.
Sources
Good to know
A mirror keeps the box up, not your history
RAID1 is good for uptime: one disk can die and the box keeps working. But it copies a deletion or ransomware to both disks at once. Add a backup that keeps older versions, on a device outside the array. RAID is not a backup: it protects against one dead disk only, so a copy off the box is still needed.
What to do
- Set up a backup job that keeps more than one version, to a USB disk or another NAS.
Sources
Good to know
Two separate disks: good for history, slower to recover
If one volume backs up the other, the scheduled copy runs behind, so a deletion or an encryption is not copied until the next run; snapshots on the backup volume keep older history. The cost: if the main disk dies you restore from the second one, and anything changed since its last run is lost. Keep snapshots on both volumes. RAID is not a backup: it protects against one dead disk only, so a copy off the box is still needed.
What to do
- Check that the backup job between the two volumes ran recently.
- Turn on a snapshot schedule on both volumes in ADM Snapshot Center (btrfs volumes only).
Sources
Good to know
Two disks in a four-bay box, two bays empty
You have room to do more than a mirror. There are three common choices, and experts split on them. For a family archive KEEP recommends the first. A bigger array in the same box is still not a backup. RAID is not a backup: it protects against one dead disk only, so a copy off the box is still needed.
Experts differ: the options
- Use the empty bays for a separate backup volume Recommended
For: A volume with its own disks protects against deletion and file-system damage that the mirror would share.
Against: You use half the raw space twice over, and you manage two volumes.
- Add disks and migrate RAID1 to RAID5 or RAID6
For: ADM can migrate online (RAID1 to RAID5 adds 1 to 14 disks, to RAID6 adds 2 to 14) and gets more usable space from the same bays.
Against: There is no way back down, the migration is a long heavy job on every disk, and the data is still in one box.
- Add a hot spare
For: ADM supports spares for RAID 1, 5, 6 and 10, and rebuilds on its own when nobody is home.
Against: It uses a bay, sits in the same chassis and does nothing for deletion or ransomware.
What to do
- Whichever you choose, back up first and replace or add disks one at a time.
- ADM migration is online but cannot go back down; Asustor warns that replacing several drives at once, or while the NAS is syncing, causes data loss.
Sources
Good to know
RAID5 on large disks
A rebuild of a big disk takes many hours, and the array has no protection left while it runs. Experts disagree on how risky RAID5 is: the middle view is that RAID5 is acceptable with a good backup and regular scrubs, and that RAID6 is the safer choice for large disks. KEEP recommends RAID6 for a family archive if you can migrate; if you stay on RAID5, keep a current backup before any rebuild. RAID is not a backup: it protects against one dead disk only, so a copy off the box is still needed.
Experts differ: the options
- Move to RAID6 (ADM migrates RAID5 to RAID6 by adding a disk) Recommended
For: RAID6 survives any two failures, so a second problem during a long rebuild does not lose data.
Against: It costs a second disk of capacity, and migration is one-way.
- Stay on RAID5 with a good backup and regular scrubs
For: Supporters argue the unreadable-sector spec is a worst-case figure and real rebuild failures are rare.
Against: Critics quote Seagate not guaranteeing a full read of the entire drive twice without an unreadable sector; a degraded RAID5 has nothing left to fall back on.
What to do
- Check your backup is current before you replace a failed disk.
- If you choose to migrate to RAID6, back up first: ADM cannot go back down.
Sources
Serious
This volume loses data if one disk fails
A RAID0 or JBOD volume gives no protection: lose one disk and you lose the volume, or part of it. ADM cannot migrate these volumes to a safer level. The only way out is to move the data off and rebuild the volume. RAID is not a backup: it protects against one dead disk only, so a copy off the box is still needed.
What to do
- Copy the data to another device first. Asustor: data must be offloaded to another storage device.
- Then create a volume with RAID1, RAID5 or RAID6 and copy back.
Sources
Worth fixing
A hot spare, but a share with no backup
This box keeps a disk as a hot spare, while at least one share has no backup. ADM supports spare drives for RAID 1, 5, 6 and 10, up to two per volume. A spare protects against a dead disk only, never against a deletion, ransomware or a lost box. A backup protects against all of those, so a backup does more than a spare. Whether a hot spare, a cold spare on the shelf or RAID6 is best is a trade-off, and opinions differ; the backup comes first either way. RAID is not a backup: it protects against one dead disk only, so a copy off the box is still needed.
What to do
- Set up a backup for every share first (ADM: Backup & Restore).
- Then decide whether to keep the bay as a spare or use it for the backup.
Sources
Worth fixing
This disk uses shingled recording (SMR)
SMR disks rewrite whole bands, slow down on long writes. If this disk is in a RAID array, a rebuild is a heavy write. Check the exact model number against the maker's list; the suffix alone is not enough. NAS-rated CMR lines include WD Red Plus, Seagate IronWolf and Toshiba N300. RAID is not a backup: it protects against one dead disk only, so a copy off the box is still needed.
What to do
- Look up the exact model on the maker's CMR/SMR list.
- Plan to replace it with a CMR disk, one disk at a time, after a backup.
Sources
Good to know
KEEP does not know whether this disk is SMR
This model is not in KEEP's list of checked SMR models. That does not mean it is CMR, and being on Asustor's compatibility list does not either: that list had SMR models (as of 2020). Look the exact model up on the maker's page.
What to do
- Find the model number in ADM Storage Manager and look it up on the maker's CMR/SMR list.
Sources