Warning! The instructions below assume that you have basic skills to manipulate hard disk drives. Any physical damages to hard drives may cause permanent data loss. If you are not completely sure you can work with hardware, please, turn to professional data recovery services.
Attention! This article contains details about NAS state after its resetting to factory defaults. Please read the article carefully for information about data recovery from a failed device after resetting.
The most common causes of data loss from NAS storages include:
Hard drive failure;
Electrical damage or overheating of the storage;
Software failure or faulty firmware update;
Accidental deletion of important information by user mistake.
Data recovery chances from NAS storages depend on the NAS model and data loss causes.
As NAS devices don't provide low-level access to data you'll have to disassemble the storage and connect its hard drives to a recovery computer before you start data recovery. Preparation steps include:
Eject the hard drive from the device;
Make sure the hard drive is workable. If the data loss was caused by a logical failure such as files deletion or NAS re-initialization hard drives remain not damaged. In cases of any physical damages caused by, for example, electrical damage or overheating hard drives fail and data recovery is possible only after hard drive repair. Bring your NAS to a specialized data recovery laboratory to avoid data loss;
Connect the workable drive to a recovery PC (as described in 3. article;
Recover your information with any of or software products.
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. These software have embedded tools for RAID recovery. Other UFS Explorer products work with RAID systems via plug-in modules. All the software employ powerful mechanisms to allow you to achieve maximum possible recovery result and are 100% reliable to guarantee complete safety of the data stored on your NAS. For more detailed information, please, go to .
Note: Do-it-yourself data recovery makes sense only when:
To prepare the hard drives for data recovery follow these steps:
- Shut down your NAS;
- Remove the drives through the front panel: open the door and eject the enclosures;
- Mark the drives (Left/Right for Linkstation and Top/Bottom for Terastation) to re-assemble the device in the same order;
After NAS drives are successfully connected to a recovery PC you may start data recovery.
LinkStation and TeraStation NASes have equal data layout:
Figure 1. NAS drives in UFS Explorer RAID Recovery.
Actual view will depend on software version and edition;
Actual drives sizes will depend on the NAS model;
Identified partitions will depend on the NAS model and software version and edition;
Extended partition (partition with sub-partitions) is a container and is not mentioned further on.
Each NAS drive has the same structure of the partitions:
Boot firmware partition. This partition contains files to boot embedded custom Linux OS (no user data here);
Firmware partition. This partition contains embedded Linux system files such as executables, configurations etc. (no user data here);
Swap partition. This partition is used by embedded Linux OS to extend RAM (memory swapping);
Data (storage) partition. This partition contains user files. For RAID configurations data partitions of each drive are combined into software RAID virtual device.
Note: Depending on the vendor and the model NAS can contain from two and up to four partitions on each drive. Data partition is the largest partition (95..99% of the entire disk space) and it has no sub-partitions.
For RAID1 valid XFS file system will appear on the data partition of each NAS drive. For SPAN or RAID0 the first drive will contain 'SGI XFS' on the data partition and the second one – 'Raw partition'.
Diagnostics and data recovery
To diagnose and virtually rebuild your NAS configuration follow these steps:
Step 1. Connect both drives to a recovery PC
For mirror RAID1 configuration you may connect one drive.
In cases when
a) the drive doesn't show SGI XFS file system on the data partition;
b) SGI XFS file system is unreadable (reports read error);
c) you can't find some of the files available on the device after data loss.
- connect both drives for further diagnostics.
Step 2. Check the file system on data partitions
You will get one of the following results:
Both drives contain SGI XFS file system on data partitions (see Fig.1)
NAS is configured to RAID1 (mirror). The file system is readable on both drives. Data recovery is possible from any of the drives.
Both drives contain Raw partitions indicated with a gray icon (see Fig.1)
The file system seems to be destroyed or NAS worked as iSCSI target. In this case your NAS requires professional data analysis and data recovery services.
One of drives contains SGI XFS and the other one – Raw partition (see Fig.1)
NAS was configured to RAID0 (default configuration) or Span. The drive with SGI XFS file system will be referred to as 'first' and with Raw partition as 'second'. Explanations as to further analysis you will find in Step 3.
After the analysis you can start recovery from any of RAID1 drives. If you fail to recover your data, please, use professional data analysis and data recovery services.
Step 3. Open SGI XFS file system on data partition of the first drive
You will get one of the following results:
File system opened and you can see "share" folder:
NAS must have been configured to SPAN. In rare cases this result appears for RAID0 with stripe size over 64KB;
File system is unreadable:
NAS was configured to RAID0.
If you run the scan for at least partial file system reconstruction, you'll get a more precise result. If the recovered files have valid contents it is JBOD or RAID 1 configuration, if file contents are invalid this is RAID0.
Step 4. Verify RAID configuration
For SPAN (JBOD):
Check contents of "share" folder on the first drive;
If the folder contains files all of them can be opened using hex preview tool of UFS Explorer;
If all files can be opened, the second drive can be an unused or a failed component of RAID1. Try to recover the data from the first drive;
If the files or folders are missing or some files can not be opened this is a SPAN configuration.
SPAN configuration on TeraStation and LinkStation products doesn't fit to data partition and can not be aligned without knowledge of XFS file system or professional analysis.
Figure 2. Build RAID tool icon in UFS Explorer.
Figure 3. RAID Builder tool in UFS Explorer.
Step 5. Analyze the reason for RAID0 emergence and assess recovery chances
RAID1 configuration provides for data recovery from one of its drives. SPAN configuration requires professional assistance in data recovery. RAID0 configuration requires analysis and reconstruction.
The reasons for RAID0 emergence on your NAS storage include:
NAS re-configuration. After re-configuration of NAS storage lost data remain recoverable. You should assemble the storage as described in Step 4 instructions. All good files emerge in 'share' folder of Virtual RAID. If you don't find the files scan the Virtual RAID for lost information.
NAS resetting. After virtual re-assembling of NAS storage as described in Step 4 Virtual RAID will display a new default file system and contain an empty 'share' folder. Recovery chances depend on the original NAS configuration:
Original RAID0 (stripe set)
If the previous configuration was set as "maximum speed and capacity" and the drives weren't swapped before resetting, NAS file system was formatted. To recover lost information run 'Data Recovery' scan enabling 'File system reconstruction' option.
If the drives were swapped before NAS resetting rebuild RAID as described in Step 4 but with reverse drives order. As a result you will get Virtual RAID with Raw partition. To recover lost information run 'Data Recovery' scan enabling 'File system reconstruction' option.
Original RAID1 (mirror)
If the previous configuration was with half of full capacity and redundant the data sustained more serious damage as a new XFS file system was written with different parameters. Ordinary file system reconstruction won't give expected results.
Scan the second drive of NAS storage, the one with Raw data partition. If this doesn't provide any good result, it's recommended to use professional data recovery services.
File systems remain almost equal. To recover the data destroy invalid XFS superblocks produced with RAID0 format. After this re-assemble RAID as SPAN and run file system reconstruction. Note that modification of disk structures and span aligning will require knowledge of XFS file systems structures or professional data recovery assistance.
NAS resetting destroys some of on-disk structures after what some files, folders or file names could be lost permanently. It's recommended to analyze the entire tree of "reconstructed file system" for files you are looking for. Some files and folders can appear under "[Parent unknown]" virtual folder with numbers in file/folder names.
In case of any physical damages it's strongly recommended to bring your NAS to a specialized data recovery laboratory in order to avoid data loss.
If you feel unsure that you are capable of 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.
For data recovery professionals SysDev Laboratories offer expert NAS storage analysis on commercial basis.
Last update: 16.04.2012