NAS Data Recovery – Possible But Difficult

Network Attached Storage or NAS is a popular solution to store files that need to be shared among many users. It is mainly found in companies but because of cheap hard drives and high storage capacity it is also used in home environments. While in companies NAS is used mainly as a centralized storage, at home it is usually used as multimedia storage for movies, images, MP3 files and similar content. Even if there is only one user accessing the storage, NAS offers many advantages over other storage solutions. Cheaper models usually provide support only for non-redundant systems like JBOD or RAID0 while more advanced and expensive NAS models support also one or more RAID modes where the data is distributed across the drives for improved availability and performance.

NAS is in fact a small independent computer with disk array. You don’t see the NAS as a typical computer—you only access the data via network. Usually SMB/CIFS protocol is used in Windows or NFS in Linux/Unix environment. On user’s computer NAS is seen as one ore more disks. Because NAS is seen as a black box, many users don’t pay attention to the fact that this only a computer which can fail. Failed NAS causes problems to all users who depend on the data stored there. Therefore, experienced system administrators treat NAS systems with necessary care. When failure happens there is usually a backup solution and if for some reason it is not available you may have a problem. NAS data recovery usually means RAID data recovery which is considered as a complex recovery process and is therefore quite expensive. Data from NAS devices is as safe as is the RAID array inside it.

The main part of NAS is disk array. Theoretically one hard drive would be enough. But because of the requirement for higher capacity and higher availability typical NAS system consists of an array of disks. This array is usually used as RAID – Redundant Array of Inexpensive Disks. Each NAS includes an embedded computer which controls the disk array and provides network access to the users. This embedded computer runs a special operating system (embedded Linux is often used) which provides RAID functionality (if there is no dedicated hardware RAID controller), user interface for settings and administration, network access via standard protocols (NFS, SMB/CIFS, FTP, Web, etc.), and additional functions that are specific to each NAS model. In most cases you will have only one partition, but this depends on your needs and NAS software. Many partitions can be useful to separate data for different users. Each data partition can have different file system which can be useful if you are using different operating systems.

There are also few open source NAS projects based on Linux or FreeBSD. They offer flexibility, customization and low price of the system. But you still need basic PC hardware and at least one hard disk to run NAS—an old desktop computer will do the job. A popular open source solution is Free NAS.

Typical NAS hardware is very similar to that of a file server but in most cases it is not possible to use NAS for any other purpose than network access and file storage. There are at least two reasons that may prevent you from expanding the functionality of NAS system. The first one is the architecture of NAS which is a closed system. Normally you can not access the operating system except through standard network protocols (HTTP, FTP, SMB/CIFS). The second reason is the processor that runs the system. It is designed to be capable of handling network requests and data manipulation not anything else. Of course, there are NAS systems that allow shell access and can be expanded but this is not the primary function of NAS which is network attached storage. And finally, any additional service may endanger the primary function and data integrity.

NAS Data Recovery

NAS data recovery is possible but it can be as complex as with RAID arrays or even more. When there is a problem with NAS you should first determine the nature of the problem. The problem may be hardware related or file system related. Hardware related problems are further divided into hard drive failures and embedded computer problems. Because there are many NAS manufacturers (Buffalo, WD, HP, Linksys, Netgear, QNAP just to name few of them) where each has its own hardware/software solution and because NAS is considered as black box—it is not open except for the drive exchange, you can not simply replace faulty component. Therefore, if there is a hardware problem you should replace the whole electronics in order to access the disks. Most NAS systems include tools to repair broken RAID arrays but advanced NAS data recovery is beyond the scope of NAS operating system.

To recover data from single disks standard data recovery software can be used, but RAID systems need more sophisticated tools because the files are distributed across all the disks. If you have configured NAS disks as a standard RAID system (for example RAID 5) then you have at least theoretical chances to recover the data without the original NAS hardware. However, you would need to know RAID parameters to be able to recover the RAID array. This data was set when you have created RAID and if the NAS system is inaccessible then you can only guess. Additionally there may be special or proprietary approaches on how the disks are organized that can make NAS data recovery difficult. To successfully recover files and data from a broken NAS you better leave this task to professionals which have plenty of experience with disks and RAID arrays. They can quickly determine if and how the data could be recovered.

Fortunately, there are many RAID data recovery companies that will have no problem with NAS systems and RAID recovery. If you have problems with NAS and you need the data then this is the safest option. NAS recovery means checking both single disks and RAID as system. Theoretically you could get another NAS of the same model and swap the drives. But this is risky—before the disk swap you would have to configure it exactly as the failed one. But even with the same configuration there are still chances that this will not work as expected or even worse—you could destroy the data on the disks.

To avoid problems with NAS and data loss you should treat it as a computer which can fail. If any hard drive in the RAID fails the NAS will continue to operate—until the next drive will experience problems. Single drive failure causes only array degradation, but the files continue to be accessible. Hard drive failures should send warning messages and most NAS systems have some kind of management where you can define warning settings. RAID presents additional reliability comparing to single hard drive but ignoring warning about disk failure will put you on the lower level of reliability equal to the reliability of remaining individual drives in the array.


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