Articles: Networking

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Basic Functionality

The main purpose of this NAS is to store files, of course. It can perform this service by using internal HDDs as well as external storage devices. The internal HDDs can (and should) be united into a RAID array. The NAS supports a maximum of four disks, so there are a few types of disk subsystem you can build: individual disks, a JBOD array with the combined capacity of the installed disks, a RAID0 for combined capacity and higher performance, and RAID1/5/6 for fault tolerance. You can even build multiple arrays limited only by the number of disks. For example, you can use two disks in a RAID1 for reliable storage of backups and documents, and unite two more disks into a RAID0 for higher performance. For a fault-tolerant 3-disk RAID5 a fourth disk can be a spare one. In this case, if one of the main disks fails, the spare disk will be used automatically to restore the array.

In some cases the arrays can be augmented without losing data. For example, you can add one more disk into a JBOD or join a single disk into a RAID1.

Before being used in an array, a disk must be scanned for bad blocks. You can also check out the file system on disk volumes. SMART technology is supported. Besides viewing information about the HDDs, you can run their integrated tests.

Disk volumes you create can be encrypted with AES256 but this has a negative impact on performance. The encryption key may be specified by the user and not stored on the NAS. In the latter case, the administrator must enter it after turning the NAS on in order to use a volume. Additionally, you can change/save/restore the key.

When the HDDs are formatted by the NAS, some of their disk space is allocated for system purposes. We lost about 1.5GB (two 500GB partitions for the OS and 500GB for the swap file). The main volume with data uses an EXT3 file system.

Besides disk arrays, you can use iSCSI technology to implement a local storage resource on your PC. In this case, there appears a virtual SCSI controller on the PC, and its disks are connected via LAN cable. Like with ordinary HDDs, the controller’s disks can be partitioned, formatted, etc. The client part is available as standard in Windows Vista and in most Linux distributions. For Windows XP you can use third-party client software. Take note that this usage implies that the volume is connected to one client exclusively. That is, the data are only available for reading and writing from one computer at a time. The iSCSI virtual disks are physically stored in special files on the NAS’s disk volumes.

The NAS’s disk resources communicate with the world via two Gigabit Ethernet interfaces. The employed controllers support jumbo frames up to 9000 bytes, which has a positive effect on the speed of writing. A DHCP client is supported, and the NAS can also act as a DHCP server. As there are two LAN interfaces, you can choose one of three operation modes for them: autonomous interfaces, fault-tolerant mode, and load balancing mode. Among additional network features there are a DDNS client, IP address filter, and automatic locking of the client if the user is attempting to guess the password to the various services.

The main network-based file access protocol today is SMB/CIFS. The NAS can work in a workgroup on a Windows network or be included into an AD domain. This service can be disabled when necessary (if you need only FTP or NFS, for example).

User authentication is done using an internal database or via the domain. User groups and quotas are supported.

When the first volume is formatted, the NAS automatically creates a few common system folders such as Public and Qmultimedia. The administrator can later change the access rights for them but cannot delete them. Besides choosing user, group and guest account rights for each folder, you can individually hide a folder from the network environment and set the oplocks parameter for it. For each volume you can enable a network recycle bin, which is handy. But don’t forget that it only works for a Windows network. Files are deleted immediately and irrecoverably via FTP.

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