Data Recovery from Enterprise RAID: Dell, HP, NetApp, Synology
Enterprise RAID systems are more complex than typical home NAS. Each manufacturer has its own architecture, proprietary metadata, and specific tools. Data recovery from these systems requires specialized knowledge and equipment.
In this article, we'll examine the most widespread enterprise RAID platforms and specifics of their recovery.
Dell PowerEdge (PERC Controllers)
Dell PowerEdge servers use PERC (PowerEdge RAID Controller) controllers – one of the most widespread enterprise RAID controllers on the market.
PERC Generations
| Model | Generation | RAID levels | Max. disks |
|---|---|---|---|
| PERC H700 | 11G | 0,1,5,6,10,50,60 | 32 |
| PERC H710 | 12G | 0,1,5,6,10,50,60 | 32 |
| PERC H730 | 13G | 0,1,5,6,10,50,60 | 32 |
| PERC H740 | 14G | 0,1,5,6,10,50,60 | 64 |
Common Problems
Foreign Configuration: After controller replacement or disk move, array reports "Foreign Configuration". Controller doesn't recognize metadata from different controller.
Failed Controller: Controller fails, but disks are fine. Without compatible controller, array is inaccessible.
BBU (Battery Backup Unit) Failure: Battery backup failure can cause data loss from write cache.
Predictive Failure: Controller marks disk as "Predictive Failure" – warning before failure. Important to monitor and respond.
Recovery Specifics
Controller replacement: Ideal is same controller model with same firmware version. Controller can then import "Foreign Configuration" and array is accessible again.
Import Foreign Config: Procedure in BIOS configuration utility:
- Ctrl+R during server startup
- Foreign View → Import
- Verify configuration
- Reboot
Virtual reconstruction: If compatible controller unavailable, array can be reconstructed virtually using PC-3000 RAID or similar tools.
Case Study: Dell R720 with PERC H710
Situation: Dell R720 server with 8× 2TB disks in RAID 6. Controller failed after power surge.
Diagnostics: Disks fine, controller burned.
Solution:
- Found compatible PERC H710
- Disks connected to same ports
- Import Foreign Configuration
- Array accessible, data recovered
Success rate: 100%
HP ProLiant (Smart Array)
HP ProLiant servers use Smart Array controllers – another very widespread platform.
Smart Array Generations
| Model | Generation | Note |
|---|---|---|
| P410/P411 | G6/G7 | Older, still common |
| P420/P421 | Gen8 | With FBWC |
| P440/P441 | Gen9 | Higher performance |
| Smart Array SR | Gen10/10+ | Latest |
HP Specifics
ADG (Advanced Data Guarding): HP name for RAID 6. Same principle, different name.
FBWC (Flash Backed Write Cache): Instead of battery, uses flash memory to preserve cache during power failure. More reliable than BBU.
ORCA vs ACU:
- ORCA: Option ROM Configuration for Arrays – BIOS-based configuration
- ACU: Array Configuration Utility – more advanced tool
Common Problems
Cache Failure: FBWC or BBU failure can cause loss of unwritten data.
License Issues: Some advanced features (like RAID 6) require license. Without license, controller refuses to recognize array.
Interval Write Protect: After cache failure, controller switches to write-protect mode. Data protected, but performance drastically drops.
Recovery Specifics
Metadata location: HP stores metadata in multiple places – on controller and on disks. This helps during controller replacement.
Controller compatibility: Compatibility between generations is limited. P420 cannot import array from P440.
Cache data recovery: If FBWC contains unwritten data, it can sometimes be recovered.
Case Study: HP DL380 Gen8 with P420i
Situation: 6× 600GB SAS disks in RAID 5. Two disks failed within 24 hours (from same batch).
Diagnostics: Degraded + failed = array offline.
Solution:
- Sector copy of all 6 disks
- Analysis – second "failed" disk only had URE, data readable
- Virtual RAID 5 reconstruction
- Data extraction
Success rate: 97% data recovered
NetApp (WAFL/ONTAP)
NetApp is premium storage system with proprietary architecture. Data recovery from NetApp is significantly more complex than from regular RAID.
NetApp Architecture
WAFL (Write Anywhere File Layout): Proprietary file system optimized for storage. Not compatible with standard tools.
RAID-DP: NetApp variant of RAID 6 with double parity. Proprietary implementation.
Aggregates and Volumes:
- Aggregate: Group of disks forming storage pool
- Volume: Logical unit in aggregate
- LUN: Block device in volume
Why NetApp is Specific
Everything is proprietary: File system, RAID implementation, metadata format – nothing is standard. Regular recovery tools don't work.
Snapshots: NetApp supports file system level snapshots. Helps with recovery but complicates structure.
Deduplication: If deduplication enabled, data stored fragmentedly. Reconstruction is more complex.
Common Problems
Disk Shelf Failure: Failure of entire shelf (disk enclosure) – power, SAS expander.
Aggregate Offline: Aggregate goes offline due to metadata corruption or multiple disk failure.
Volume Corruption: File system corruption in specific volume.
Recovery Specifics
ONTAP recovery tools: NetApp has proprietary recovery tools. Some require support contract.
Aggregate reconstruction: Requires knowledge of NetApp architecture and access to specialized tools.
Requires specialization: NetApp recovery is one of most complex. We recommend only specialized facilities.
Case Study: NetApp FAS2240
Situation: Small NetApp with 12 disks. After firmware update, aggregate offline.
Diagnostics: Firmware bug corrupted aggregate metadata.
Solution:
- Firmware rollback not possible
- Manual WAFL structure reconstruction
- Data extraction from volumes
Success rate: 85% data recovered (some fragments lost)
Synology NAS
Synology is popular NAS platform for SMB and enterprise. Uses proprietary SHR RAID and Btrfs file system.
SHR (Synology Hybrid RAID)
What is SHR: Proprietary RAID implementation over Linux mdadm. Allows combining disks of different sizes.
SHR-1: Tolerates 1 failure (similar to RAID 5) SHR-2: Tolerates 2 failures (similar to RAID 6)
DSM and Btrfs
DSM (DiskStation Manager): Synology operating system. Based on Linux.
Btrfs: Modern file system with snapshot, deduplication, and self-healing support.
ext4: Older variant, still used on some models.
Common Problems
Multiple Disk Failure: Same problem as other RAID – failure of multiple disks.
Volume Crash: Btrfs or ext4 corruption after power failure or error.
DSM Update Gone Wrong: DSM update failed and system won't boot.
Recovery Specifics
Linux mdadm compatibility: SHR is built on mdadm. Disks can often be connected to Linux system and array reconstructed.
Btrfs recovery: Standard Linux tools for Btrfs recovery (btrfs-tools).
Superblock locations: mdadm stores superblocks at specific positions. Important for array identification.
Synology Recovery Procedure
- Connect disks to Linux system
cat /proc/mdstat– displays recognized arraysmdadm --assemble --scan– automatic assembly attempt- If automatic fails, manual assembly:
mdadm --assemble /dev/md0 /dev/sdX /dev/sdY ... - Mount volume and copy data
Case Study: Synology DS1819+ with SHR-2
Situation: 8-bay NAS, Btrfs. Three disks failed after power surge (faulty UPS).
Diagnostics: 3 disks failed (SHR-2 tolerates 2), but NAND chips OK.
Solution:
- Failed disk diagnostics – PCB damage
- Electronics repair on 2 disks
- Sector copy of all 8 disks
- mdadm assembly
- Btrfs recovery
Success rate: 99% data recovered
QNAP NAS
QNAP is Synology competitor with similar architecture.
QNAP Specifics
QTS operating system: Similar to DSM, also Linux-based.
RAID implementation: Standard Linux mdadm + proprietary layer.
Snapshot Vault: Similar to Btrfs snapshots on Synology.
Common Problems
Very similar to Synology:
- Multiple disk failure
- Volume corruption
- Firmware issues
- ext4 corruption
Recovery Specifics
Recovery procedures almost identical to Synology – mdadm based, Linux compatible.
Recovery Complexity Comparison
| System | Complexity | Required tools | Typical success |
|---|---|---|---|
| Dell PERC | Medium | PC-3000 RAID, spare controller | 80-95% |
| HP Smart Array | Medium | Proprietary, PC-3000 | 80-95% |
| NetApp | High | Specialized, WAFL tools | 70-90% |
| Synology | Medium-low | Linux, mdadm, btrfs-tools | 85-95% |
| QNAP | Medium-low | Linux, mdadm | 85-95% |
What We Need to Know for Recovery
When contacting us about enterprise RAID recovery, it's helpful to prepare:
1. System/controller type
- Dell PERC H7xx, HP Smart Array Pxxx, NetApp FAS, Synology DS...
- Firmware version (if known)
2. RAID configuration
- RAID level (5, 6, 10...)
- Stripe size (if known)
- SHR/SHR-2 for Synology
3. Number and type of disks
- Total number of disks
- Individual disk capacity
- HDD vs SSD
- Serial numbers (if available)
4. What happened (timeline)
- When problem appeared
- What preceded it
- What error messages
- What steps you've already taken
5. Disk order
- Physical positions in shelf/server
- Slot labels
- Wiring photos
FAQ
How long does enterprise recovery take?
Usually longer than regular RAID:
- Dell/HP: 3-7 days
- NetApp: 5-14 days
- Synology/QNAP: 3-7 days
Depends on capacity, disk condition, and problem complexity.
Can you come on-site?
Yes, for critical cases we offer on-site diagnostics. Usually more efficient to bring disks to us – we have all tools in one place.
Is remote diagnostics possible?
Partially. We can analyze logs, event history, and SMART data remotely. For full diagnostics, we need physical disk access.
What if we don't have manufacturer support?
Not a problem. Our recovery is independent of support contract with Dell, HP, or NetApp. We work directly with data on disks.
Why DataHelp for Enterprise Recovery
Experience with All Platforms
25 years experience with enterprise storage from all major manufacturers.
Specialized Tools
PC-3000 RAID, VNR, proprietary tools for NetApp and other platforms.
24/7 for Business Critical
Servers don't wait until Monday. We're available 24/7 for critical cases.
References
We work with companies of all sizes – from SMB to large corporations and government institutions.
Need Help with Enterprise RAID?
Whether you have Dell, HP, NetApp, Synology, or another platform – we can help. Diagnostics is free.
24/7 Hotline: +420 775 220 440 For businesses: 24/7 emergency service