I talked with the folks over at iXSystems about FreeNAS, and TrueNAS, along with their line of hardware at VMWorld. For a SMB, the ability to re-purpose old hardware for something as important as network storage, is a great way to keep costs low. To also have a community of help is an important part. With Enterprise-grade features, and an Open source license to create a RAID storage array for backups, replication, and file sharing. You will be able to set it up for internal, or external use.