RAID 1 Failure Recovery

We deliver engineering-grade recovery for RAID 1 mirrors across home, SME and enterprise environments—2-disk mirrors through multi-pair mirrored sets inside servers, DAS and NAS. We regularly handle escalations from enterprises and public-sector teams.

How to send drives:
Label each disk with its bay/slot order and enclosure/controller make/model. Place each disk in an anti-static bag, cushion well in a padded envelope or small box, include your contact details, and post or drop them in. We clone every member first and only work from those clones (forensic, write-blocked handling).

UK NAS brands we most often see (with representative popular models)

1. Synology – DiskStation DS224+, DS423+, DS723+, DS923+, DS1522+; RackStation RS1221+, RS4021xs+

2. QNAP – TS-464, TS-473A, TS-873A, TVS-h674; rack TS-x53DU/x73AU

3. Western Digital (WD) – My Cloud EX2 Ultra, EX4100, PR4100

4. Seagate / LaCie – LaCie 2big/6big/12big, Seagate IronWolf NAS enclosures

5. Buffalo – TeraStation 3420/5420/6420, LinkStation 220/520

6. NETGEAR – ReadyNAS RN424, RN524X, RN628X

7. TerraMaster – F2-423, F4-423, F5-422; U-series racks

8. ASUSTOR – AS5304T, AS6604T, LOCKERSTOR 4/8

9. Drobo (legacy) – 5N2, B810n

10. Thecus – N5810PRO, N7710-G

11. iXsystems (TrueNAS) – Mini X/XL, R-series

12. LenovoEMC (legacy) – ix2/ix4, px4

13. Zyxel – NAS326, NAS542

14. D-Link – DNS-320L, DNS-340L

15. Promise – Vess/VTrak NAS families

Rack servers commonly deployed with RAID 1 (representative)

1. Dell EMC PowerEdge – R540/R640/R650/R750, T440/T640

2. HPE ProLiant – DL360/DL380 Gen10/Gen11, ML350

3. Lenovo ThinkSystem – SR630/SR650, ST550

4. Supermicro SuperServer – 1029/2029/AS-series

5. Fujitsu PRIMERGY – RX2540, TX2550

6. Cisco UCS C-Series – C220/C240

7. IBM/Lenovo (legacy) – x3650 families

8. NetApp / HPE StoreEasy (Windows NAS servers) – StoreEasy 1460/1660/1860

9. Dell Precision workstations – 5820/7820/7920 (OS+logs mirrored)

10. HP Z-Series – Z4/Z6/Z8

11. Areca HBA builds – ARC-1883/1886

12. Adaptec by Microchip – ASR-71605/8405/8805

13. Promise VTrak DAS mirrors

14. Infortrend EonStor (DAS mode)

15. HighPoint NVMe mirror deployments

Why RAID 1 fails (and how we approach it)

RAID 1 mirrors duplicate blocks across members, but real-world mirrors often drift: one side continues to receive writes while the other intermittently drops; rebuilds start from a stale copy; or both members degrade mechanically/electronically. Correct recovery requires:

• Selecting the correct epoch (the truly “last good” side) using journals/USN, file-system intent logs, and modification timelines.

• Imaging both members and, where each has unique readable areas, building a block-level union image to maximise completeness.

• Never rebuilding on originals; all work is on read-only clones.

Professional RAID 1 workflow (what we actually do)

1. Intake & documentation – serials, slot order, controller/NAS configs, SMART baselines.

2. Clone every member first – hardware imagers (PC-3000, Atola, DDI) using unstable-media profiles: head-select, zone priority, progressive block sizes, reverse passes, adaptive timeouts.

3. Epoch & side selection – compare $MFT/USN (NTFS), APFS object map/snapshots, EXT journal, XFS log to identify the member with the latest consistent state; avoid the stale or partially-rebuilt side.

4. Block-union strategy – where each clone has unique good sectors, construct a union image (map of best blocks per LBA), preserving provenance.

5. Filesystem/LUN repair on the image – NTFS/ReFS, APFS/HFS+, EXT/XFS/ZFS/Btrfs; journal/intent replay, B-tree & bitmap repair; no writes to members.

6. Encryption handling – BitLocker/FileVault/LUKS/SED volumes decrypted on the clone with valid keys; otherwise plaintext carving only.

7. Verification & delivery – SHA-256 manifests, sample-open testing (DB/video/mail), secure handover.

Top 75 RAID 1 faults we recover — with technical approach

A. Member/media failures (HDD)

1. Clicking on spin-up (head crash): donor HSA matched by micro-code → translator rebuild → head-map imaging prioritising good heads/zones.

2. Spindle seizure/no spin: spindle swap or platter migration; validate SA copies; clone readable surfaces.

3. Stiction (heads stuck): controlled release; pre-amp test; short-timeout imaging to avoid re-adhesion.

4. Platter scoring: donor heads; isolate damaged surface; partial clone with skip map.

5. Weak single head: disable failing head; per-head zone cloning; fill from good mirror where possible.

6. Excess reallocated/pending sectors: reverse/small-block passes; reconstruct FS around holes.

7. Servo wedge damage: interleaved reads; skip wedges; accept gaps, fill from partner.

8. Pre-amp short: HSA swap; bias verification; image.

9. Translator corruption (HDD): rebuild from P/G-lists; restore LBA; clone.

10. SA copy-0 unreadable: recover from mirror SA; module copy/repair; proceed.

B. Electronics/firmware/bridge

11. PCB/TVS/regulator burn: replace TVS/regulator; ROM/EEPROM transfer; safe power; clone.

12. Wrong donor PCB (no ROM move): move ROM/adaptives; retrain.

13. USB-SATA bridge failure (external mirrors): bypass to native SATA; image.

14. Encrypted bridges (WD/iStorage): extract keystore; decrypt image with user key/PIN.

15. FireWire/Thunderbolt bridge resets: limit link speed; stabilise host; image.

C. SSD/NVMe mirror specifics

16. Controller lock/firmware crash: enter SAFE/ROM; admin resets; L2P (FTL) extraction; clone namespace.

17. NAND wear/ECC maxed: majority-vote multi-reads; channel/plane isolation; partials filled from partner.

18. Power-loss metadata loss: rebuild FTL/journals; if absent, chip-level dumps & ECC/XOR/interleave reconstruction.

19. Thermal throttling resets: active cooling; reduced QD; staged imaging.

20. Namespace hidden/missing: enumerate via admin; clone each namespace.

D. Mirror drift, stale copies & rebuild issues

21. Split-brain (both online, diverged): compare journals/USN/APFS snapshots; choose latest consistent side; avoid mixed epochs.

22. Stale member promoted during rebuild: detect epoch jump; roll back to pre-rebuild point using logs.

23. Rebuild from wrong source (controller bug): parity not applicable; identify direction via timestamps; select correct donor.

24. Interrupted rebuild (power fail): many files half-old/half-new; use file-system intent log to choose version per file.

25. Automatic resync after cabling fault: treat resynced target as suspect; validate against logs before using.

E. Controller/HBA/metadata

26. Foreign config conflicts (LSI/Adaptec): dump all generations; pick last coherent; ignore stale metadata.

27. Intel RST fakeraid confusion: assemble manually from raw members; bypass driver.

28. Areca/Promise metadata mismatch: parse headers; select consistent generation.

29. Write-cache loss (BBU failure): choose stripe versions via journal consensus (even on mirrors, journals matter).

30. Sector size mismatch (512e/4Kn): normalise during virtual build; re-align partitions.

F. NAS stacks (mdadm/LVM/Btrfs/ZFS)

31. Synology mdadm mirror degraded: clone both; assemble md on clones; mount LVM/EXT4 or Btrfs readonly.

32. QNAP mdraid + LVM2 drift: assemble epoch-consistent md set; reattach LVs; export.

33. Btrfs metadata duplication corrupt: use surviving metadata mirror to rebuild root; recover.

34. ZFS mirrored vdev with one bad label: import readonly; zdb to map blocks; copy files.

35. DSM/QTS update rewrote md superblocks: select pre-update generation; mount on clones.

G. Partitioning & boot metadata

36. GPT primary lost; secondary intact: restore GPT from backup; verify FS bounds.

37. Hybrid MBR/GPT (Boot Camp) mismatch: normalize to GPT; fix boot chain.

38. Protective MBR only: recover GPT from secondary; mount volumes.

39. Hidden OEM/Recovery partitions complicate mounts: image all; mount individually; export.

H. Filesystems on mirrors

40. NTFS $MFT/$MFTMirr divergence: reconcile; replay $LogFile; repair $Bitmap; recover orphans.

41. ReFS metadata error: rollback to consistent CoW epoch via shadow copies.

42. APFS object map damage: rebuild OMAP/spacemaps; enumerate snapshots; export.

43. HFS+ catalog/extent B-tree corrupt: rebuild trees; graft orphans.

44. EXT superblock/journal issues: use backup superblocks; fsck with journal replay; copy out.

45. XFS log corruption: xfs_repair with logzero when indicated; salvage.

46. ZFS mirror but pool won’t import: zpool import -F -o readonly=on; copy healthy files.

I. Encryption on top of RAID 1

47. BitLocker (OS or data) on mirror: require recovery key; decrypt on the union image; repair FS.

48. FileVault (APFS) on mirror: passphrase/recovery key required; decrypt clone; rebuild container.

49. LUKS/dm-crypt: header/backup header; PBKDF → decrypt on image; mount readonly.

50. SED (self-encrypting) drives: unlock with credentials; otherwise only raw carving of plaintext remnants.

J. Administrative / human errors

51. Mirror broken; one disk reused/quick-initialised: deep scan reused disk; reconstruct pre-init contents; merge with partner.

52. Accidental “convert to RAID-0/5” attempt: ignore new metadata; assemble prior mirror epoch.

53. Disk order swapped in caddy: use serials and FS continuity to restore order.

54. “Initialize disk” clicked in OS: ignore new label; recover old partition map on clone.

55. Cloned wrong direction during replacement: identify source/target by timestamps; pick correct side.

K. I/O path & environment

56. SATA/SAS CRC storms (bad cable/backplane): rehost; stabilise path; clone; discard inconsistent logs.

57. Expander link flaps: map enclosure topology; lock stable lanes; image.

58. Power brownouts under load: bench PSU; safe rails; clone.

59. Thermal throttling (NVMe mirror): active cooling; reduced QD; staged imaging.

60. USB/UASP DAS mirrors reset: fall back to BOT; powered hub; image.

L. Virtualisation & datastores on RAID 1

61. VMFS datastore header damage: rebuild VMFS; stitch VMDKs; mount guests.

62. VMDK descriptor missing; flat present: regenerate descriptor; attach.

63. Hyper-V AVHDX chain broken: fix parent IDs; merge diffs on clone.

64. Thin-provisioned volumes: honour allocation maps; avoid zero-filled noise.

65. iSCSI LUN mirror: recover target mapping; mount LUN; export filesystems within.

M. Application-level salvage

66. PST/OST oversize/corrupt: low-level store repair; export to new PST.

67. SQL/SQLite with good WAL: replay WAL on clone; export consistent DB.

68. Large MP4/MOV unplayable: rebuild moov/mdat; GOP re-index; re-mux.

69. Photo libraries (Lightroom/Photos): repair catalog DB; relink originals from image.

70. Sparsebundle (Time Machine) on mirror: rebuild band map; mount DMG; restore.

N. Edge cases & legacy mirrors

71. Windows Dynamic Disk mirror (LDM): rebuild LDM database; mount volumes.

72. Apple Software RAID (legacy HFS+): parse Apple RAID headers; assemble virtually.

73. mdadm metadata version conflict: select coherent superblock set; assemble degraded; copy out.

74. Btrfs RAID1 with metadata/data mismatch: salvage using redundant metadata copies; btrfs-restore.

75. ZFS boot mirror, one label missing: reconstruct from remaining labels; import readonly.

Supported drive brands inside arrays

Seagate, Western Digital (WD), Toshiba, Samsung, HGST (Hitachi), Maxtor (legacy), Fujitsu (legacy), Intel, Micron/Crucial, SanDisk, Kingston, ADATA, Corsair, Sabrent, PNY, TeamGroup, and more. We handle SATA, SAS, SCSI (legacy), NVMe/PCIe, M.2, U.2/U.3, mini-SAS, USB/Thunderbolt enclosures, 512e/4Kn sector formats, and hybrid/fusion configurations.

Why choose Sheffield Data Recovery

• 25+ years focused on RAID and enterprise storage.

• Clone-first, read-only workflow with advanced imagers and donor inventory.

• Deep stack expertise: controllers/HBAs, NAS mdadm/LVM layers, filesystems, hypervisors.

• Forensic verification (SHA-256 manifests, sample-open testing).

• Free diagnostics with clear, evidence-based recovery options before work begins.

Contact our Sheffield RAID 1 engineers today for a free diagnostic. Package the drives safely (anti-static + padded envelope/small box, labelled by slot/order) and post or drop them in—we’ll take it from there.