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Mass NAS: Typical data organization and peculiarities of data recovery

The modern computer market provides an ample supply of NAS storages which, depending on the retailer, may slightly differ in firmware, settings, actual data layout and other features, but, on the whole, most of them have have similar data organization: a NAS typically consists of from one to several disks which may be organized into a complex RAID system.

Therefore, major data recovery techniques applied to NAS devices are usually based on the principles of data recovery from complex RAID systems. This article gives helpful information about common NAS storages and data retrieval from them using Buffalo TeraStation, Iomega, Synology and other similar solutions as examples.


Data organization

NAS devices primarily serve as shared storages providing access to data over a local network. In general, most of them have common storage structure and data organization. The actual data layout, however, depends on the NAS vendor and embedded configuration.

Storage structure

Each NAS disk arranges data on four disk partitions:

  • Firmware-reserved partition. This partition contains technical information used by On 1 TB TeraStation, for example, this partition is 0.6 GB in size, identified as 'Linux native' and formatted with the SGI XFS file system. It is available on the 1st and the 2nd NAS disks only.
  • Swap partition. This partition contains swap for NAS firmware.
  • Data partition. This partition stores user data. On 1 TB TeraStation, for example, it is a 232 GB partition identified as 'Linux native'. The actual size depends on NAS settings.
  • Padding partition. This partition is used to unify data partition size regardless of the actual number of disks. The size depends on the disk model. On 1 TB TeraStation it is identified as 'Linux native' but contains no file system.

Disk partitioning style is standard DOS-style (MBR-based) and is readable by any software.

RAID configuration and data organization

Depending on the configuration RAID offers several possible data organization methods for Data partitions:

  • RAID5. The most widely-used configuration. In the RAID5 mode user data is located across Data partitions of all the four disks. Usual parity distribution is backward-dynamic (left-symmetric). The stripe size depends on the settings (usually it is 64 KB). The disks order for RAID is consequent: the 1st disk of NAS is the 1st disk of RAID, etc. The data partition on TeraStation, for example, is formatted as SGI XFS while on Synology – as Ext3.
  • RAID0. User data is usually arranged as a single full-capacity storage or a pair of RAID0 stripe sets with two independent partitions (different 'share' virtual folders on NAS). Both contain the same file system type but different data.
  • RAID10 or RAID0+1. The mirror of two RAID0 stripe sets or stripe set of two mirrors. User data is arranged the same way as in RAID0 but only one 'share' and both stripe sets contain the same information.
  • JBOD. Data partitions are concatenated to yield maximum storage capacity. User data is-*3 spanned across all the data partitions.
  • Individual drives. In NAS drives that are not organized in RAID each data partition relies on an independent file system.

Before you start data recovery from your NAS you should identify the actual configuration of the storage. For more information about RAID systems, please, refer to RAID: structure and recovery article.

Before you start data recovery from your NAS you should identify the actual configuration of the storage. For more information about RAID systems, please, refer to RAID: structure and recovery article.

When is recovery required?

Due to their evident advantages NAS storages have already become an essential part of everyday work for home users and SMBs. NAS vendors began to offer quite cost-efficient solutions which increased their availability on the market. Despite the enhanced reliability of these storages they are still exposed to failures resulting in storage inaccessibility or even data loss. 
Most common data loss causes include:

  • Loss of a NAS link;
  • Offline array or 'four red lights';
  • Data corruption due to power outages;
  • Firmware crash or failed boot;
  • Disk(s) failure;
  • Controller failure;
  • Electrical or mechanical damages.

User errors causing data loss include:

  • Faulty firmware update resulting in the reset of embedded RAID settings;
  • Files deletion;
  • Rebuilding embedded RAID configuration on live data resulting in disks re-formatting.

If you are sure that NAS disks didn't sustain any physical damage and remain workable, you may start data recovery following the instructions given below. If the disks have any physical defects caused by mechanic, thermal or electric damage, it's strongly recommended to have your data recovered in a specialized data recovery laboratory. 

For efficient recovery from NAS storages SysDev Laboratories advise their UFS Explorer software. UFS Explorer RAID Recovery was specially designed to work with complex RAID systems. UFS Explorer Professional Recovery offers professional approach to data recovery process. Other UFS Explorer products work with RAID systems via plug-in modules. All the software products apply powerful mechanisms, allowing to achieve maximum recovery result and are 100% reliable, guaranteeing complete safety of the data stored on your NAS. For more detailed information, please, go to https://www.ufsexplorer.com/products.php.

Getting started

As NAS devices don't provide low-level access to data, before you start data recovery, you have to disassemble the storage and connect its hard drives to a computer. To do this:

Mark the order of NAS disks!

  • Remove hard disk drives from NAS;
  • Identify the interface type of the drives: modern NAS use SATA drives; older storages may still use PATA/IDE drives;
  • Connect the disks to a personal computer.

If the computer used for recovery doesn't provide sufficient number of disk adapter interfaces you can:

  • Install an additional PCI hard disk adaptor;
  • Use USB hard disk adaptors;
  • Attach the disks one-by-one and make full disk images. This solution is recommended provided that you have enough free disk space.

Warning: Turn off the computer and unplug the power cable before you install any PCI device or connect/disconnect SATA/PATA drives to avoid electric damage!

Having ensured access to the NAS data you can start the data recovery process.

Data Recovery

Among all data recovery software we advise UFS Explorer RAID Recovery for your NAS as a software specially designed to work with complex RAID configurations.

The entire data recovery process with UFS Explorer RAID Recovery requires a few simple steps:

  • Get low-level access to the NAS disks: connect them to a computer for recovery or save disk images as described above. Get direct access log in with the rights of a local system Administrator;
  • Identify the type of RAID configuration: refer to 'RAID recovery' in the user manual for instructions;
  • Open the disks: refer to 'Operations' in the user manual;
  • If RAID doesn't require reconstruction, start data recovery from the Data partition of the NAS drive (Data partition is usually the largest one): refer to 'Operations: Lost files recovery' in the user manual;

If RAID requires reconstruction you have to build a virtual RAID storage before you start data recovery: refer to 'RAID recovery: Building RAID' in the user manual for instructions. The result of RAID reconstruction appears as a 'Virtual RAID' in the list of storages. Refer to 'Operations: Storages tree navigation' in the user manual for more information. When the virtual reconstruction of RAID is completed, you may start data recovery as described in 'Operations: Lost files recovery' of the user manual;

  • On completion of all the required operations you can copy your files to a safe location.

Final notes

In case of any physical damage it's strongly recommended to bring your NAS to a specialized data recovery laboratory in order to avoid data loss. 

If you feel unsure about conducting data recovery operations from your NAS by yourself or not confident about RAID configuration in your NAS, feel free to use professional services provided by SysDev Laboratories

Data recovery professionals of SysDev Laboratories offer expert NAS storage analysis on a commercial basis.

Last update: 05.07.2018