FreeNAS logo

FreeNAS Linux RAID

In Blog, Recovery of the day, Server/RAID Array Recovery Case Study by Administrator

9/9/2017 – 4 Disk RAID-5 FreeNAS – Multiple HDD failures

Work has recently been completed on a four disk RAID-5 network attached storage (NAS) device. The four disks came from a computer using FreeNAS. These were comprised of three different models of HDD and of different capacity.

The owner of the RAID had reported that the NAS had been performing badly, with the computer hanging and crashing. He reported that at least one disk, and potentially a second, had been excluded by the RAID controller and had been reported as failed. The customer had also made his own attempts on the RAID to try and restore the data from it. These attempts had failed, and he reported that as a result of his actions the RAID would not longer report the correct volume size (3000GB).

Hard disk drive details:

Manufacturer: Seagate / Hitachi / Samsung

Model: 1TB / 1.5TB / 2TB disk to create a 3TB RAID-5 volume.


All four HDDs were imaged (cloned) using the appropriate data recovery equipment (DeepSpar Disk Imager). Three of the HDDs had bad sectors. Once disk imaging was complete attempts were made to rebuild the RAID by emulating the RAID configuration. This includes establishing the starting location (offset) for each disk, the disk order, and stripe size.

There was inconsistency across the four HDDs suggesting that there had been a ‘bad rebuild’ of the RAID set. No complete Linux Ext3/4 filesystem could be located. It was necessary to rebuild the filesystem locating the necessary iNode structure to recreate the original folder and file name. This proved more challenging than usual as the HDDs in the RAID had been previously used for other purposes. This meant there was residual data on the HDDs which was not relevant to the RAID rebuild.

Nearly all of the data was recovered successfully. However, there was some data loss to files which had been recently modified/created in the 10 days prior to the RAID failure.

The customer was provided CDR’s file list software to examine the recovery to ensure that the recovery met their requirements. On approval of this, the data was prepared for return.

In this case, the data related mainly to the customer’s personal data (e.g. family photographs) which he had saved for several years on the HDDs.


Customer review:

The following review can be found on CDR’s Google Business listing.

CDR – Manchester Data Recovery Services is undoubtedly the best, most qualified and trusted data recovery service in the UK. To a lot of people, either in personal or business life; their data is incredibly important. When the worst does happen, AND you find your backups haven’t been running for a few months due to an unknown fault; you want a trusted and reputable company to work explicably carefully and efficiently in order to have the best opportunity of recovering your data.

As a relatively technical person, when the filesystem on one of my RAID5 arrays became corrupted, I conducted sensible attempts to try and recover my filesystem and restore access to my array. The more actions I took, the more I saw the filesystem become less recognisable, fully corrupt and finally completely DISAPPEARED. I had 2TB of data on this 3TB RAID array, and it had completely gone – vanished, unrecognisable by any reasonably reputable software recovery tools and what was an incredibly anxious time was quickly swapped with hope after talking to Dr John C. Reid at Cheadle Data Recovery.

To be honest, after reading the reviews; CDR Manchester was the first and only recovery service I had called, however I was highly sceptical anything could be done to recover any of my data. I thought I must be their worst type of client (someone relatively technical with previous successful recovery attempts of other people’s data on an informal scale) and this attempt had completely and utterly failed. John spent over an hour talking me through on the phone the steps that can be taken, and he left me without a shadow of a doubt feeling that he was the absolute best person to attempt the recovery of my data. I immediately got in the car and drove the disks straight up to Manchester, and within a timeframe much sooner than anticipated the early investigation had started into the feasibility of recovering my data.

I received regular updates on my recovery attempts, and once I thought some very recently modified files (before the corruption) were missing, CDR took additional manual recovery attempts and managed to return absolutely everything. Absolutely unbelievable considering from further investigation, 3 out of the 4 drives had faults on them.

Finally, well within the timeframe given on turn-around, I had received an email with an incredibly detailed directory and file structure of all my data, along with the health of each individual file – all complete, and something I thought I would never see again. CDR Manchester provides all your data on an optional brand new, modern USB3 portable hard drive.

I hope I never have to talk to CDR Manchester for a personal reason again; however the journey from chaos to full recovery was made better by the regular updates and support from CDR Manchester, and I for one would recommend CDR Manchester no matter how technical or non-technically minded you are. The professional approach to customers, business and service is exceptional and how CDR is run as a business is an absolute inspiration to any business-minded person.
Thank you very much for your efficiency.