Netgear ReadyNAS 1100

We've always found most half-depth rack appliances excessively noisy but not so with the 1100 as even with six cooling fans at the rear it's surprisingly quiet. During testing we had the unit next to us on the bench and never found it intrusive. The hard disk backplane and motherboard are also separate units making it a cinch to remove the latter. Furthermore, the Linux-based RAIDiator OS is implemented on Flash memory so you can buy a diskless unit.