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NAS and RAID - what are the options?
NAS and RAID - what are the options?
Time icon20 February 2019, 13:02 pm

Networked storage is an external file server that can be easily managed by the user. With a NAS, you can easily provide any amount of storage capacity for a PC network. A major advantage is that the stored data can be read and processed with any computer in the network. Access from mobile devices such as tablets or smartphones is also possible.


SSD or SATA hard disk storage for a NAS system?

In addition to the transfer speed of the hard disk, the data transfer speed of the network is also decisive. At present, SSD storage media are still very expensive, systems with SATA technology are offered much cheaper.


NAS with RAID system

In a "reduntant array of independent disks" several hard disks are connected to each other. The data can be stored securely and without loss. Depending on the specific requirements in the respective network, different options can be selected. For all RAID systems, the storage capacities of the individual hard disks should be as large as possible. 

  • RAID 0 – Two or more hard disks are connected. This system allows fast access to the stored data, but is limited by the network speed. If one hard disk fails, all data is lost.
  • RAID 1 – As with RAID 0, at least two hard disks are merged. All data is stored redundantly and is available on another storage medium in the event of a failure of individual hard disks in the network. In this case, the system automatically reads the file from the correct storage location on a functioning hard disk.
  • RAID 5 – At least three hard disks are connected to the network. While RAID 1 results in a loss of 50% of the storage capacity, RAID 5 deducts the volume of a hard disk from the total storage. If two hard disks fail, all data is lost. If only a single hard disk fails, this is not relevant for the preservation of the stored data.
  • RAID 5+ Spare – Ideal for a network of at least four hard disks. Data stability is ensured by the memory of two hard disks, which is subtracted from the total volume. In the event of failures, the hard drive network is restored immediately and the stored data is retained. However, if further failures occur during this phase, the security of the data is not guaranteed.
  • RAID 6 – Four or more hard disks are used. For data security, the storage of two hard disks is used, the same conditions apply as with the RAID 5+ Spare System. Overall, the speed is somewhat reduced, but the data will be preserved even if two hard disks fail at the same time. 


Tips for a RAID system as NAS

Defective hard disks should be replaced as soon as possible. In this way, users contribute significantly to the security of the stored data. RAID systems do not replace backups! Data of great importance should always be stored at least twice. If the RAID system is infected by a virus or if errors occur in the program, important data can be lost. 


SCSI & SAS for network storage

SCSI describes standardized interfaces and protocols that enable data transmission between the individual devices in the network. SCSI stands for "small computer system interface". 

The "serial attached SCSI" (short: SAS) is a serial interface in the computer with a transfer rate of 3, 6 or 9 Gbit/s. The serial attached SCSI is a serial interface in the computer with a transfer rate of 3, 6 or 9 Gbit/s. The serial attached SCSI is a serial interface in the computer with a transfer rate of 3, 6 or 9 Gbit/s. Communication between the individual devices is made possible by the following protocols: 

  • SSP – SAS SCSI Protocol
  • STP – Serial ATA Tunneling Protocol
  • SMP – SAS Management Protocol

Half or full duplex connections are possible, depending on the type chosen by the user. Line bundling is not possible with SATA, SAS also offers the option of using Dual Channel when SSD hard disks are connected in the network. While SAS can be connected as a multi-initiator, SATA is only available as a single host or for a multi-lane connection.