How to recover data from a broken RAID array on an LSI 3ware 9750 card
This post walks through recovering data when a RAID storage array fails, specifically on the LSI 3ware 9750 controller card. It covers RAID 0, RAID 1, and RAID 5 setups. Useful if you run a home or small server with a hardware RAID card.
RAID is a way of combining multiple hard drives so they act as one — either for speed, safety, or both. RAID 1 mirrors your data across two drives, so if one fails you still have a copy. RAID 5 spreads data across three or more drives and can survive one drive dying. RAID 0 is the risky one: it splits data for speed but loses everything if even one drive fails.
The LSI 3ware 9750 is a dedicated RAID controller card common in servers and NAS boxes. This guide explains step-by-step what to do when the array shows a degraded or failed status — how to check which drive is the problem, how to pull data off safely, and how to avoid making things worse. For Mac mini server users, this is most relevant if you have an external RAID enclosure or a NAS attached to your setup.
Key points
- RAID 1 survives one drive failure; RAID 5 also survives one drive failure — RAID 0 does not survive any failure
- Always make a backup copy of remaining drives before attempting any recovery
- Use the 3DM2 or tw_cli utility to check array status on the LSI 3ware 9750
- Do not write new data to a degraded array — it can overwrite what you're trying to save
- Rebooting or swapping drives carelessly during recovery can cause permanent data loss
Quick term guide
- array
- The group of hard drives working together as a single RAID unit.
- LSI 3ware 9750
- A hardware RAID controller card — a dedicated chip that manages multiple hard drives in a server.
- server
- A computer that stores files and shares them with other devices in your home.
- hardware
- The physical parts of a computer that you can touch.
- degraded
- A warning state where one drive in the RAID has failed but the system is still running on the remaining drives.
- Mac mini server
- A Mac mini used as an always-on computer for files, apps, backups, or automation.
- Mac mini
- A small desktop computer made by Apple.
- ping
- The time (in milliseconds) it takes for a signal to travel from your device to another and back — lower means faster response.