Data Recovery from a 6 Disk Dell FreeNAS ZFS RAID 0

A Case Study in ZFS Data Recovery

System: 6 Disk Dell RAID 0
Operating System: FreeNAS
File System: ZFS

Location: London / Essex

Outcome: Successful recovery

We received a call from a customer with a crashed Dell 6 disk RAID 0 server. The server was configured using FreeNAS and running the ZFS file system. Zpools was unavailable and the customer told us their system was currently with another data recovery company who were unable to progress the recovery.
The PERC H700 RAID controller is very common in these systems.

The RAID controller was a PERC H700, running in RAID which was presenting a large volume to the FreeNAS system. This is the incorrect way to setup such as system because by not allowing FreeNAS to access the individual disks and utilise RAIDZ, it is unable to utilise the redundancy ZFS provides. If a hardware RAID controller is required it should be setup as HBA.
The hard drives arrived with us: they were 5x2TB Seagate drives (Constellation) and 1xToshiba 2TB.
All the drives were cloned, but one was found to have firmware issues which once fixed also showed the drive was suffering from bad sectors. This drive was transferred to specific hardware which was able to successfully read most of these bad sectors. Eventually an excellent clone was obtained, with only approx 1000 bad sectors not read.
Once all the hard drives had been cloned they were re-introduced back into the system.
Information from the PERC controller card showed 4 drives online, one foreign and one ready – the Dell had kicked out the failed drive and the whole RAID 0 had failed.
We therefore copied and re-coded the Dell RAID information (located at the rear of every drive) back to the hard drives (by copying and modifying the RAID management info from the original failed drive because it had been untouched and was original).
The drive was re-introduced to the system and the RAID 0 would not come back online.
The system was then booted into FreeNAS, but although the 12TB disk could be seen, no volumes or pools could be located. Nothing we did in FreeNAS gave any access to the data.
We then replaced the FreeNAS system which was installed onto a USB stick with a Ubuntu system.
Running command line actions in Ubuntu was crucial in getting this data recovered.

The installation of Ubuntu allowed us to use tools which could see and access the 12TB ZFS volume. It showed heavy data corruption and the data folders were inaccessible.
We then installed a customer ZFS version for Ubuntu from a repository and executed various terminal commands to find and mount the ZFS partition. We then repaired the data corruption.
The server’s data, now repaired and accessible, was recovered to an external drive.

> Links

Main RAID and Server Data Recovery Page
Main Dell RAID and Server Recovery Page

data, Dell, recovery, zfs

Data Clinic Reviews

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Jacob Greenwood

14:38 30 Mar 18

5* customer service! Recovered my father's book from an old drive, also retrieved some long forgotten about photos. Simply cant put a price on something like that.

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12:21 30 Jul 18

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15:56 10 Apr 13

We've used Data Clinic twice now - once for my son's laptop which held all his University work and suddenly seemed to just die, that was recovered with ease. And then secondly in connection with work when our office computer system backups were somehow corrupted. These people really know their stuff - they are very helpful and professional and quick! Thanks so much for everything.

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11:33 09 Dec 16

Happy to recommend Data Clinic to anybody that suffered Data Loss on storage Media. The guys were extremely helpful and knowledgeable and made the recovery of our valuable data a stress free experience.

George Thorpe

12:19 20 Feb 14

My company provides IT support to approximately 60 Yorkshire based companies ranging from small 10-15 users up to Enterprise sized organizations. Due to disk failure a client recently lost their entire database. We contacted Data Clinic and within hours a representative was onsite, several hours later the drive was returned, again in person by Data Clinic Manchester. I would not hesitate contacting them again, outstanding service in a market that can mean life or death to a business. 10 stars if there was an option!

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21:02 25 Oct 18

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David Tett

14:36 24 Aug 18

Sent them a 4tb WD Red hard drive to recover. They quoted me £588 incl VAT and recovery media. I was a bit sceptical so I asked for it to be returned. First they sent me the wrong hard drive (a 500GB WD Blue). Not too careful about data protection then. When I eventually got the drive back it had been totally stripped and outer casing binned (would have been nice to know about this beforehand). I decided to send it to Curry's PC World. They quoted £90 + recovery media. All data recovered and both hard drives returned within a week. What more is there to say.

Elle Sweet

22:12 20 Aug 18

Awful communication, I was constantly chasing them for updates on my device. My device was with them days before work was started on it. The data this company couldn’t retrieve was later retrieve by Apple. Waste of a £110.

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