http://www.sun.com/servers/x64/x4600/specifications.jsp
> Key Specifications
> - 4U Rackmount
> - 4 to 8 single or dual-core AMD Opteron Processors
> - Up to 128GB* (with footnote at the bottom *When 4GB DIMM is available)
> - Up to 4 hot-swappable SAS HDDs 　←ココ
> - Runs Solaris 10 OS, Red Hat and SuSE Linux, Windows Server, VMware