Network Attach Storage (NAS) and Storage Area Network (SAN) units will usually contain multiple hard disks configured as a RAID array. These are attached to the network and present storage space for use by other computers on the network.
Such units were at one time the preserve of the enterprise level market, mostly used by large companies and data centres. With the price of storage dropping over the last 10 years, NAS units have become more common across sectors, with many being used in the home, often as a media server rather than using a computer to act as the server. It is important that these units are configured correctly and their health monitored to avoid problems which can only be resolved through data recovery.
Network Attached Storage
A NAS system once configured is expected to operate with little or no intervention and act as central file storage area, which can be used by any computer attached to the network whatever the operating system, such as Windows, OSX, Linux, BSD etc. These range from simple systems, which allow any user on the network to access the data, through to multiuser systems with storage quotas, to cater for all market levels.
Many of the most recent NAS systems can be configured to automatically backup data to a cloud server. These provide an efficient system for centrally storing data, without the need to share data from an individual computer, which can cause complications, especially when that system needs rebooting. A NAS is intended to act as a continually available file server.
Storage Area Network
A SAN system, usually only seen at enterprise level, is most prevalent in data centres. These are configured to present disk space to a specific machine as though it were a hard disk directly attached to that machine. This is particularly useful when multiple rack mounted servers are being used, where installing additional hard disks would be inefficient and complicate the process of ensuring no data is lost.
These are most likely to be attached to a 10Gbe network in order to provide the kinds of data transfer required. A SAN system will usually contain data from multiple servers, with no knowledge of the underlying file system being used. These are usually meticulously maintained, often with fail over servers in place, making data recovery due to failure very rare.
Correct Configuration and Data Recovery
For a NAS system it is important that when they are configured, that the RAID level used is appropriate for providing redundancy. It is tempting to use a RAID 0 striped configuration as it provides the most efficient use of disk space, but this increases the risk of data loss, as the failure of any disk will cause the NAS to fail. Less efficient configurations are recommended from the most secure RAID 1 mirroring through to RAID 5 which provides a good compromise between data redundancy and disk usage.
At DiskEng we have extensive experience of recovering data from both NAS and SAN systems, with a high level of success. It is usually only multiple catastrophic disk failures or a misguided attempt at recovering the data which can lead to severe or even total data loss.