Capacity

How much storage can the NAS provide? There are two major issues: the number of disks and the logical organization of those disks. EX: if the NAS can hold two 4 TB disks, the capacity of the NAS can be 8 TB. But if those disks are configured as RAID 1 - mirroring - those two disks simply copy each other; so, the total usable capacity would only be 4 TB, but the storage would be redundant.

Form Factor

Where will the NAS be installed? The two principal form factors are rackmount and tower (standalone). An enterprise NAS can use a 2U or 4U rackmount form factor for installation into an existing data center rack. A tower or self-contained NAS can be a good choice for deployment in smaller department data closets or even on desktops.

Performance

How many users will the NAS support? It takes a finite amount of network and internal computing power to handle a storage request from the network and then translate that request into actual read/write storage tasks within the NAS. A busy NAS will demand higher levels of performance and internal caching to provide greater storage I/O and efficiently support more simultaneous users. Otherwise, users will need to wait longer (lag) for the NAS to service their storage request.

Connectivity

How will the NAS connect to users and applications? Most NAS equipment includes one or more traditional Ethernet ports for cabled network connectivity. High-capacity network connectivity is essential for busy NAS devices in enterprise data centers. NAS designed for smaller, less-demanding environments can get by with Wi-Fi connectivity, while small NAS devices for end-users might supply a USB port for direct PC connectivity.

Reliability

How can the NAS handle problems? Reliability has three major layers: the reliability of the NAS itself, the reliability of the disks installed within the NAS and the reliability of the data stored on the disks. At the NAS level, the equipment itself should be designed to provide long, continuous service at the peak expected performance level. Disk reliability depends on the disks installed in the NAS; high-quality SAS disks can offer excellent error-correction and enormous mean time between failure figures, but all disk choices should include a replacement plan. Finally, the NAS handles RAID, replication and other means of maintaining data integrity within the device, but those features must be enabled and configured.

Security

How is data protected on the NAS? Look for NAS equipment that provides native data encryption and strong network access controls to ensure that only authorized users and applications can access storage.

Usability & Features

How easily can the NAS be set up and deployed? Look for NAS equipment that is easy to deploy and configure, and consider the features and functionality included with the NAS OS/software, such as data snapshots, data backups, data replication, automatic data tiering and RAID.