NAS and SAN Technology

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.

Why Use RAID 1 Array

RAID 1 often called a mirrored array, utilises a pair of hard disk drives to provide 100 percent data redundancy by ensuring both drives contain the same data, known as mirroring. Despite hard disk drive prices being low, it is rarely seen outside of enterprise solutions, often used for high dependency systems, which are required to run 24/7.

Mirrored arrays are being seen ever more frequently for data recovery, which is because of a couple of factors discussed below. The DiskEng data recovery specialists have extensive experience in recovering data from mirrored RAID 1 systems most usually required following the failure of both disks in the array.

Data Safety Essential

The second disk stores a mirror copy of the data which ensures the highest level of data redundancy possible with a RAID array. Although it halves the potential storage capacity, using a RAID 1 array has little or no drawbacks over using a single disk, despite the requirement to write the data to two drives. Data transfer speeds when reading data may in some cases may see a small increase.

The price per gigabyte of data has dropped rapidly, making the use of RAID 1 architecture more attractive, a significant reason for a corresponding increase in data recovery requirements. Using this type of RAID in high dependency servers may be highly beneficial, but a backup plan should still be implemented in order to guard against any potential failure.

RAID 1 Re-mirror

A RAID array will remain operational following the failure of a single disk, at which point it will run in degraded mode. When a hard disk fails should always be replaced with a new one as soon as practicable, so that the data from the working drive can be re-mirrored.

Data transfer speeds have increased considerably, but at the same time overall capacities of hard disk drives has correspondingly increased. This means that re-mirroring will take a considerable length of time, at which point the data is vulnerable. If you source both hard disks from the same supplier at the same time for use in a RAID 1 array, the possibility of the second drive failing shortly after the first is significantly high. Due to the significantly increased time taken when re-mirroring modern hard disks we are starting to see a rise in the number of RAID 1 arrays which require data recovery.

Data Recovery RAID 1

If your RAID 1 array suffers a failure, which usually occurs during the re-mirroring process, it is important that you do not panic. It is important that both of the original hard disk drives used in the RAID 1 array are sent for professional data recovery. If the failure became apparent during re-mirroring it may be beneficial to supply the new hard disk drive onto which the data was being copied, as important data, vital for achieving a successful data recovery may be contained on the drive.

If the hard disk drive which initially failed is not too far out of date, it can be used by our data recovery specialists to rebuild a fully working array in the event of encountering bad sectors on the other drive. Data loss is only likely to happen in the event of both drives containing the same unreadable bad sector or when the failure of one drive is not acted upon immediately.