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This article describes general information about mass RAID-based NAS solutions on examples of Buffalo TeraStation, Iomega, Synology and other similar RAID solutions. The article describes general techniques of Data Recovery from these NAS solutions on example of using UFS Explorer Professional Recovery edition.

The sources of this article are public information, RAID specifications and our own data recovery experience.

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Copyright © SysDevSoftware, Bogdan Shulga 2007
This artical is published for educational purposes only. Any commercial use is prohibited.

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Contents

• When recovery is required?
• Getting started
• Data organization
• Data Recovery
• Final notes

When recovery is required?

The mass NAS solutions bring on market cheap enough solutions for storing Personal and Small Business data. They works nice giving you enough disk space, fast network access and many other advantages. However, making these solution cheap the vendors some sacrificing reliability of such solutions. Unexpected failure of such device may cause data inaccessibility of data loss. And often data loss is occurred between data backups or on data that has no backup at all. So lost data recovery is required.
There are set of exploitation and design-related situations when Data Recovery is required:

• NAS link loss;
• Offline array or "four red lights";
• Data corruption due to power failure;
• Firmware crash or failed boot;
• Disk(s) is out of order;
• Controller failure or out of order;
• Electrical or mechanical device damage.

There are also set of user errors, causing data loss:

• Risky firmware update causing embedded RAID array settings incompatibility and thus data loss;
• Files deletion;
• Rebuilding embedded RAID configuration on live data that may cause disks to be re-formatted.

In case embedded disks are still in workability state, data recovery is possible using techniques described below (RAID5 arrays could be recovered even with one damaged disk). In case disks are physically damaged due to mechanic, thermal or electric shock - only in-lab data recovery is possible; in case of very strong data damage of physical disks damage, it's strongly recommended to recover your critical data in specialized data recovery laboratories.
You may use any available software for Data Recovery tasks. We recommend our product UFS Explorer Professionel Recovery as NAS recovery adopted product. Sections below will contain references to data recovery with UFS Explorer Professionel Recovery.


Getting started

To start data recovery from NAS device, you have to grant Low Level access to its physical disks to Data Recovery software. To do this, you have to:

• Eject hard disk drives from NAS;
• Precise hard disk interface type (for example, TeraStation uses PATA IDE disks);
• Connect disks to personal computer.

Be sure you know disks order as they were in NAS device! In case your computer has no enough free disk adaptor interfaces, you may:

• Install additional PCI hard disk adaptor;
• Use USB hard disk adaptors;
• In case you have much free disk space - attach disks one-by-one and make full disk images (this operation is recommended).

Warning: it's strongly recommended to turn off computer completely (and unplug power cable) before you install any PCI device or connect/disconnect SATA/PATA drives to avoid computer electric damage!

After all data is made accessible, you may start with data recovery.


Data organization

In this section you will find general information about data organization on commonly used NAS solutions like Buffalo TeraStation, Iomega NAS, Synology Disk Station etc. on example of Buffalo TeraStation 1TB NAS storage. It represents most common mass NAS organization. Solutions from other vendors have minor differences on firmware, available settings, actual data layout and so on, but common data organization is similar.

Storage structure
On each NAS disk data is represented on four disk partitions:

• Firmware-reserved partition. On TeraStation it is 0.6GB, identified as 'Linux native' partition and is formatted with SGI XFS file system. Valid on 1st and 2nd disks only. Contains technical information for firmware and not contains any user data;
• Swap partition. Contains swap for NAS firmware.
• Data partition. On 1TB TeraStation it is 232GB partition, identified as 'Linux native'. Actual content depends of NAS settings. It stores user data;
• Padding partition. Not used. Its size depends of disk model. Used to unify data partition size, not depending of actual disks used. Identified as 'Linux native' but contains no file system.

Disk partitioning style is standard DOS-style (MBR-based) and could be read with any software.

RAID settings and data organization
Depending of array settings, there are few possible data organizations on Data partitions:

• RAID5. Most used configuration. Data is located across Data Partitions of all four disks in RAID5 mode. Usual parity distribution is backward-dynamic (left-symmetric). Stripe size depends of array settings (usually - 64KB). Disks order for RAID is natural (1st disk of NAS is 1st disk of RAID and so on). On TeraStation this partition is formatted as SGI XFS, on Synology - as Ext3 and so on.
• RAID0. Usually data is represented as pair of RAID0 stripeset with two independent partitions (different 'share' virtual folder on NAS). Both contain same file system type but different data.
• RAID10 or RAID0+1. The mirror of two RAID0 stripesets or stripeset of two mirrors. Data is represented like on RAID0, but there are only one 'share' and both stripesets contains same information.
• JBOD. Data partitions are concatenated to give full size. Data is spanned across al data partitions.
• Disk set. Not RAID mode. Each data partition contains independent file system.

Note: real NAS storage may contain different embedded array configuration or vendor may change data organization type for existing mode.

Before you start with data recovery, you should precise your actual array configuration and settings. For more information about RAID arrays, please refer to RAID: structure and recovery document.


Data Recovery

There are few simple steps to recover your data from NAS storage using UFS Explorer Professional Recovery:

• Grant low level access to disks: attach them to Windows PC or save disk images as described above. For direct disks access be sure you are logged in with rights of local system Administrator;
• Precise embedded array type; follow recommendations from 'Data Recovery: RAID recovery' section of user manual to precise which disks you have to connect;
• Open required disks. See 'Data Access: how to access the data' in user manual;
• If no RAID reconstruction required - use Data partition of NAS drive;
• If there are striped RAID (RAID0, RAID0+1 or RAID5) - reconstruct RAID basing on Data partitions, referring to 'Data Recovery: RAID recovery' section of user manual for details. Result would contain one or more 'Virtual RAID' virtual disks with 'unknown' partition. Use 'Find supported file system' tool as described at 'Data Access: how to access the data' section of user manual.

Now NAS is virtually reconstructed on your Windows PC. Depending of actual data damage you now may either just copy data from your 'virtual NAS' (no data damage; only hardware/firmware failure) or recover the lost information with RAW recovery tool as described in 'Data Recovery: RAW recovery' section of user manual.


Final notes

If you not sure you can recover data by yourself, it's strongly recommended to bring your NAS to specialized data recovery laboratory to avoid data loss.
In case you feel you have enough knowledge to recover data by yourself but not sure about NAS configuration, you may use SysDevSoftware data recovery services to precise your NAS configuration.
And finally, in case you are working in data recovery but have difficulties with mass NAS analysis, you may commercially use SysDevSoftware data recovery services.

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