Se você deseja usar seu computador como servidor NAS, por que não tentar FreeNAS ?
FreeNAS is a free network-attached storage server, supporting: CIFS (Samba), FTP, NFS, rsync, AFP protocols, iSCSI, S.M.A.R.T., local user authentication, and software RAID (0,1,5), with a web-based configuration interface. FreeNAS takes less than 64 MB once installed on CompactFlash, hard drive or USB flash drive. FreeNAS is currently distributed as an ISO image and in source form. It is possible to run FreeNAS from a Live CD, with the configuration files stored on an MS-DOS-formatted floppy disk. There is also a VMware disk image available.
Se não isso, eu usaria apenas o sabor do linux com o qual você se sente confortável.