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These articles provide basic information and helpful recommendations concerning data access and recovery.

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Network Attached Storages: data recovery

Network Attached Storages (NAS) became one of the best data storage solutions for home users as well as small and medium businesses. These devices are not space-consuming and at the same time capable of storing considerable amount of information, along with sharing it over a local network.

Like any equipment, NAS is exposed to failures and outages caused by numerous factors and resulting in the loss of valuable information. Yet, with the help of reliable data recovery software missing files can be restored even from the most complex NAS device.


NAS basics

Network Attached Storage (NAS) is a device aimed at storing files as well as sharing them over a local network. These storages work as small file servers and don't perform any functions like e-mailing, authentication or file management.

A NAS device consists of a control board which provides network access to data and from one to several disks that can be organized in a RAID system to extend disk storage space, increase operational speed and enhance storage reliability. Most NAS retailers like Iomega, Synology and Buffalo offer software-based RAID as a function of an embedded OS, while others, like Promise, supply hardware-based RAID.

NAS storages work with retailer-specific file systems. The most commonly used are Ext3 and XFS of special Linux editions. At the same time, such retailers as Adaptec offer BSD-based solutions (e.g. SnapOS) and use custom UFS editions. Modern NAS storages can also use various releases of the ZFS file system. The file system type of a NAS storage doesn't influence access to network files and storage operation, but rather data recovery chances in case of storage failures and data loss.

Typical NAS

Typical NAS storages can be divided into a few groups according to the complexity.

Data organization

Primarily, NAS devices serve as shared storages that provide access to data over a local network. Most NAS 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 about firmware. 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 instance, it is 232 GB partition identified as “Linux native”. The actual size depends on the 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”, yet, it has 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:

  • RAID5is the most widely-used configuration. In the RAID5 mode user data is located across the data partitions of all four disks. Usual parity distribution is backward-dynamic (left-symmetric). The stripe size depends on the settings (usually, it is 64 KB). The disk order for RAID is consequent: the 1st disk of NAS is the 1st disk of RAID, etc. Data partition on TeraStation, for example, is formatted as SGI XFS, 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 of them contain the same file system type but different data.
  • RAID10 or RAID0+1. The mirror of two RAID0 stripe sets or a 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 spanned across all data partitions.
  • Individual drives. In NAS drives that are not organized in RAID each data partition bases 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.

Preparation for recovery

Despite increased reliability of NAS storages, they are still exposed to failures and loss of valuable information. Most typical causes of data loss from NAS storages include system failures, software malfunctions, control board failures or human errors.

NAS storages don't provide direct access to their drives, thus, data recovery process requires storage disassembling and connecting its drives to a computer. Please read "HOW TO: Connect IDE/SATA drive to a PC for recovery" for the detailed instructions. Besides, when you remove NAS drives, it's recommended to mark their order with paper stickers or a soft ink marker in order to re-assemble the storage properly.

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 enhanced reliability of these storages, these days they are still exposed to failures resulting in storage inaccessibility or even data loss. 
Most common data loss cases 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 and reset of embedded RAID settings;
  • File deletion;
  • Rebuilding of embedded RAID configuration on live data and disks re-formatting.

If you are sure that NAS disks didn't sustain any physical damage and remain workable, you can 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 examined in a specialized data recovery laboratory. 

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

Last update: 20.06.2018