Servers in the 1U dual-socket rack unit space have their work cut out toppling our A-List incumbent. HP's ProLiant DL360p Gen8 offers a killer combination of top design, excellent upgradability and great value for money, and it will take a great product to dislodge it.
IBM's x3550 M4 is the latest to take on the challenge, and along with support for Intel's E5-2600 Xeons, it continues IBM's pay-as-you-grow philosophy, allowing businesses to start small and expand only when demand dictates. The standard models all ship with four SFF SAS/SATA hot-swap bays, which can be upgraded to eight bays.
This is achieved with a kit comprising a backplane for the four extra bays, to which you must add an IBM ServeRAID M1115 or M5110 controller for the four extra SAS ports. The latter goes into the dedicated PCI Express slot behind the DIMM sockets. Other drive options include three hot-swap LFF drives and a cheaper cold-swap LFF version available as a configure-to-order (CTO) model.
RAID cache options are extensive, with IBM offering standard battery backed-up memory and a choice of 512MB or 1GB flash-backed write cache modules. The review system includes the 512MB module, which brings support for RAID5 as well as mirrors and stripes.