A Synology volume showing a Crashed status does not automatically mean all data is gone - it means the storage pool can no longer guarantee data integrity in its current state and needs action before it is safe to use. The word Crashed is DSM's (Synology's operating system) way of saying a volume has reached a state it cannot recover from automatically. What you do in the next few minutes determines whether the data is recoverable. Stop writing to the NAS and read this guide before attempting any repair.
In short: A Crashed volume does not always mean permanent data loss. Degrade is survivable - replace the failed drive and rebuild. A Crashed volume caused by drive or file-system errors is not repairable through DSM's normal repair workflow. If its data remain readable, back them up before removing and recreating the affected storage. Crashed from multiple drive failures may need professional recovery. The first rule: stop writing to the volume immediately and identify the cause before taking any action.
Stop writing to the volume immediately. Avoid unnecessary writes to a crashed or read-only volume. A degraded storage pool remains accessible, but prioritise a current backup and prompt repair because redundancy has been reduced. If a crashed volume is still readable, Synology says not to power off the NAS; back up its data over the local network before following the crashed-volume removal and recreation workflow. If the data are unreadable, contact a data-recovery provider. Do not attempt to repair, rebuild, or reinitialise the volume until you understand the cause of the failure.
Understanding Synology Volume Status Levels
DSM uses different status labels to indicate how serious a volume problem is. Each has a distinct meaning and requires different action. Treating a Degraded volume like a Crashed volume (being overly cautious) wastes time. Treating a Crashed volume like a Degraded volume (being insufficiently cautious) risks permanent data loss.
| Normal | Volume is healthy. No action needed. |
|---|---|
| Degraded | One drive has failed in a RAID 5 or RAID 6 group. Volume is still readable and writable. Replace the failed drive to rebuild. |
| Critical | is DSM's overall system status for severe issues that may result in data loss; inspect the affected storage pool for its actual status. RAID 5 exceeds its tolerance after a second member failure, while RAID 6 exceeds its tolerance after a third. |
| Crashed | Volume can no longer guarantee data integrity. May be caused by multiple drive failures beyond RAID tolerance, file system corruption, or SHR/storage pool integrity failure. |
| Read-only | means the volume cannot function normally for writes. Possible causes include unsupported features after migration and hardware or file-system problems; copy readable data before following Synology's model- and cause-specific recovery procedure. |
| Unmounted | Volume cannot be mounted. |
Step 1: Identify the Cause Before Taking Action
Open Storage Manager in DSM and check the health status of each individual drive, not just the volume. Go to Storage Manager, then HDD/SSD, and look at the condition of every drive. A Crashed volume with all drives showing Normal suggests file system corruption rather than a drive failure - different problem, different fix. A Crashed volume with one or more drives showing Failed or Warning indicates drive failure as the likely cause.
Check the Synology system log. Go to Log Center in DSM and look at the System or Storage logs for error messages around the time the volume status changed. Log entries like Drive 1 failed or Volume 1 degraded provide a timeline of what happened. This log is essential for communicating the situation to Synology support or a data recovery service if you need outside help.
Step 2: The Degraded Volume Path
A Degraded volume has lost one drive in a RAID 5, SHR, or RAID 1 array. The volume is still readable and writable - your data is intact. The urgency is real (a second failure while degraded destroys data) but you have time to buy the correct replacement drive and wait for it to arrive.
Identify which drive failed (it will show a red or orange indicator in Storage Manager). Remove it and replace it with a drive of equal or greater capacity. For SHR volumes, the replacement must be at least as large as the failed drive. Do not replace with a smaller drive. Once the new drive is inserted, DSM will detect it and offer to rebuild the storage pool - accept and let the rebuild complete.
Rebuild time depends on the replacement drive's capacity and speed, system workload, drive condition, and RAID resync settings; it should not be estimated from total array size alone. During the rebuild, the volume remains accessible but performs more slowly. Do not power off the NAS during a rebuild. If a second drive fails during the rebuild, the array is lost - back up your data to an external drive before the rebuild if you have an external drive available.
Step 3: The Crashed Volume Path
A Crashed volume may result from drive failures beyond the RAID level's tolerance or from excessive file-system errors. RAID 0 has no drive-failure tolerance, while RAID 1 remains redundant as long as at least one mirrored member is operational. The data on the volume may be partially or fully unrecoverable without professional tools.
Do not reinitialise the volume. DSM's storage-pool Repair option is for Degraded storage. For a Crashed volume, follow Synology's crashed-volume procedure based on whether data remain readable and whether a drive was accidentally removed. Reinitialising wipes all data and creates a fresh empty volume - this is a permanent, unrecoverable action. Only reinitialise if you have verified your backup copy is complete and you are starting fresh intentionally.
If you do not have a current backup and need the data, contact a professional data recovery service before doing anything further. Services like Payam Data Recovery, Platinum Data Recovery, or international specialists like DriveSavers have tools to recover data from failed NAS arrays that DSM cannot access. Powering the NAS back on after a Crashed state and attempting self-repair can reduce your chances of successful recovery by overwriting sectors that would otherwise be readable.
File System Errors vs Drive Failures
If all drives show healthy status, file-system corruption is one possibility, but memory, cache, compatibility, migration, and other hardware issues must also be considered. RAID (a method of spreading data across multiple drives so the system survives a drive failure) protects you from drive hardware failures - it does not protect against file system corruption, which can happen after an unexpected power loss, a software bug, or a failed DSM update.
For an ext4 volume in Warning status, follow DSM's displayed suggestion and use the file-system check link if offered. Do not treat that workflow as a repair method for a Crashed volume. Running this on a read-only mounted volume is lower risk than running it on an actively crashed volume. On an ext4 volume in Warning status, DSM may offer a file-system check that attempts repair. Back up first where possible, because success without data loss is not guaranteed.
Unexpected power loss during writes can cause file-system errors even when the RAID members otherwise appear healthy. Follow the specific suggestion shown in Storage Manager. DSM may offer a file-system check for an ext4 volume in Warning status, but that should not be confused with repairing a Crashed volume. If DSM's repair fails, the file system damage is beyond what the built-in tool can fix.
Using Synology's Diagnostic Tools
Synology provides several diagnostic tools accessible from DSM that help determine whether recovery is possible without external help. The S.M.A.R.T. test in Storage Manager gives a per-drive health assessment. Run a Quick Test first; the time required varies with drive capacity and system activity. and look at the attributes section - Interpret SMART attributes using the drive manufacturer's definitions and thresholds, DSM's reported health status, and whether relevant counts are increasing; a universal greater-than-zero failure rule does not apply.
The Scrub function in Storage Manager runs a data integrity check on the storage pool, comparing parity data to stored blocks and repairing any inconsistencies it finds. Run data scrubbing as maintenance on supported healthy storage pools. A degraded pool must be repaired before scrubbing resumes, while a crashed pool is removed from the scrub schedule. On a Crashed volume, scrub cannot run - the volume is already past the point where scrub is applicable.
When to Call Professional Data Recovery
Professional data recovery is worth considering when: the volume is Crashed due to multiple simultaneous drive failures, DSM's built-in repair fails or makes the situation worse, the data has no recent backup and is critical, or the drives themselves show physical failure symptoms (clicking, grinding, or not spinning up).
Multi-drive NAS recovery costs vary widely by provider, drive count, fault type, damage, urgency, and required parts; obtain a written assessment and quote. Reputable Australian services include Payam Data Recovery and Platinum Data Recovery. Before calling, document the drive failure timeline from DSM's log, note the RAID type and number of drives, and do not attempt any further repair actions - each failed attempt reduces the chance of successful recovery.
How to Prevent This in Future
A UPS (uninterruptible power supply) connected to your NAS is the single best prevention for file system corruption. Improper shutdown can cause file-system errors, and Synology recommends enabling compatible UPS support to reduce that risk. A compatible, correctly configured UPS can keep the NAS operating briefly so it can save data, stop services, unmount volumes, and enter Safe Mode; actual runtime depends on the UPS and attached load.
Regular S.M.A.R.T. testing and storage scrubs catch early drive degradation before it causes a volume crash. Synology's DSM can be configured to run S.M.A.R.T. tests on a schedule - DSM can schedule SMART tests to monitor supported drives and report possible failure; use Synology's current test guidance and do not assume every failure will be predicted in advance. Enable the Send notifications when storage health changes option so you receive an email when a drive enters warning status, not after it has already failed.
Finally, a current backup to a separate location is the ultimate protection. A RAID array protects you from a drive failure. It does not protect you from simultaneous drive failures, ransomware, accidental deletion, or physical destruction of the NAS. The 3-2-1 backup rule - three copies, two media types, one offsite - remains the right framework even when you have RAID redundancy locally.
Related reading: our NAS buyer's guide and our Synology brand guide.
Related reading: our NAS explainer.
See also: our complete Synology NAS Australia guide.
Can I recover data from a Crashed Synology volume myself?
It depends on the cause. An ext4 volume in Warning status may offer a file-system check, but Synology's current guidance says a volume already Crashed because of file-system errors cannot be repaired through that workflow. If the crash was due to multiple drive failures beyond RAID tolerance, Self-repair attempts may worsen some failure scenarios. For critical data that are unreadable after failures beyond RAID tolerance, consult a professional before attempting reconstruction. For critical data on a multi-drive failure scenario, For critical unreadable data, consult a specialist recovery provider and ask how it preserves or images the source drives before reconstruction.
My Synology shows one drive failed and the volume is degraded. Is my data safe?
Yes, for now. A single-drive failure in a RAID 5, SHR, or RAID 1 volume leaves the data intact and accessible. The urgency is that a second drive failure while degraded will take the volume to Crashed status. Replace the failed drive as soon as possible and let the array rebuild. Confirm that the exact replacement drive is suitable for the NAS and that the specific NAS model supports hot-swapping; otherwise power down before replacement. After installation, select Repair in Storage Manager unless a supported Auto Repair configuration was already enabled.
How long does rebuilding a degraded Synology RAID take?
Rebuild speed depends on drive capacity and NAS processor speed. Estimate rebuild time from the capacity and expected operating speed of a single drive, then account for workload, resync settings, and drive condition; total storage-pool size alone is not a reliable basis. A four-drive RAID 5 set using 4 TB drives has 16 TB nominal raw capacity and approximately 12 TB nominal RAID capacity before system and file-system overhead; rebuild duration cannot be inferred from that capacity example alone. The NAS remains accessible during the rebuild with reduced performance. Do not power off the NAS during the rebuild process.
DSM is offering to Repair my Crashed volume. Should I do it?
It depends on what caused the crash. The storage-pool Repair option is documented for Degraded storage, not as a generic action for a Crashed volume. For a Crashed volume, follow Synology's cause- and readability-specific procedure before removing or recreating any storage. Before clicking Repair, confirm the cause of the crash in the Storage Manager logs and verify whether drives are physically failed or just showing a software status issue. If you are unsure, do not click Repair on a Crashed volume without a current backup in hand.
Will Synology support help recover data from a crashed volume?
Synology's support team can assist with diagnosing the cause of a crash and providing guidance on DSM's repair tools, but they cannot recover data from physically failed drives - that requires physical media examination that only specialist recovery labs can perform. Standard Australian support is available through Synology's support request and LiveChat channels; eligible On-Site Service customers also have phone and email access to local technical experts. Submit a ticket via the Synology support portal with screenshots of Storage Manager and the system log, and Response time varies by support channel, service entitlement, workload, and issue severity.
Is RAID 6 significantly better protection than RAID 5 for a 4-bay NAS?
Yes, for a NAS that stores important data. RAID 6 uses two drives for parity rather than one, which means it can survive two simultaneous drive failures without data loss. RAID 5 can only survive one. During repair, RAID 5 cannot tolerate a second member failure, whereas RAID 6 can tolerate two failed members before data loss occurs. For a NAS storing data you cannot afford to lose, RAID 6 or SHR-2 is the more defensible choice on a 4-bay or larger NAS. The cost is one additional drive's worth of usable capacity.
Australian Buyers: What You Need to Know
Payam Data Recovery is Australia-based and offers NAS/RAID recovery. Platinum Data Recovery is a US provider with a laboratory in Los Angeles, not an Australian service. International services including DriveSavers and Ontrack can also handle Synology arrays if no suitable local service is available. Australian NAS and RAID recovery costs vary widely with the provider, number and capacity of drives, logical versus physical damage, required donor parts, urgency, and complexity; obtain a case-specific written quote.
Replacement drives for a Synology NAS are available from Mwave, Scorptec, and PLE. Seagate IronWolf and WD Red Plus are the standard recommendations for consumer and SMB Synology NAS builds. Australian Consumer Law applies to drive purchases, covering you for warranty and manufacturing defect claims beyond the manufacturer's standard warranty period. When replacing a failed drive, keep the failed drive until the rebuild is complete and verified - do not discard it until you have confirmed the rebuilt array is healthy.
Want to understand RAID protection levels and which to choose for your NAS? The RAID explained guide covers RAID 1, 5, 6, and SHR with recommendations for each use case.