Marketed as a four-bay personal cloud appliance, the NAS540 is Zyxel's offering in the tricky crossover market covering both demanding consumers and price-sensitive small businesses. The leading NAS vendors all want a share of this action which means stiff competition for the NAS540 which, although well specified, falls short in a couple of key areas. A good startA compact and affordable desktop storage appliance, the NAS540 sells for around £180 ex VAT without disks (around $270, AU$350) and is little bigger than the four 3.5 or 2.5-inch drives it's built to hold. It also looks very smart thanks to a curved cube design with a removable access panel over the storage held on by magnets.Take this panel off and underneath are four bright orange plastic caddies with snap-in fixings to allow standard 3.5-inch SATA disks to be secured without the need for screws. Opt for 2.5-inch disks, however, and you'll need to get the screwdriver out.