Areca

These NAS units are the largest around, offering five HDD bays at a minimum and ten or more in many cases. They are typically geared towards advanced users who need plenty of storage space, and many are supplied in rackmount cases for use in industry and large-scale businesses. These units are not sold with hard disks so you'll need to add your own – it's best to get matching models and capacities, especially if you plan on using RAID.

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Direct Attached Storage or DAS is an external storage device that is connected directly to a server or workstation without a network device in between (ie there is no hub, switch or router required) using USB, Firewire or eSATA for example. This direct connection ensures fast access to data. A DAS will work as though the hard drives are internally connected, meaning drives can be partitioned, formatted and set up like any other internal hard drive or raid array. These DAS devices are available for standalone desk or rack mounting.
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Direct-attached storage or (DAS) is storage which is directly attached to the device accessing data from it, Opposed to storage accessed over a computer network or shared Network of devices. These are common types of storage products which are external boxes/enclosures which house inside hard drives, solid-state drives (SSD), optical disc drives, the storage range from a simple Single HDD/SSD to devices which hold multiple storage devices.

A Host Bus Adapter (HBA) is an expansion card that plugs into a PCIe slot on the motherboard and provides fast, reliable non-RAID communication between the host system and the storage devices.

A RAID controller card is similar to an HBA, but can also add redundancy (RAID) for your data, help optimise performance, reduce latency, or even make smart decisions on whether to store data on an HDD or an SSD cache, depending on user needs.