1) LSI 630J is not listed as "Certified for Windows Server 2012 R2 Storage Spaces". See:
Technically this means you'll have zero support after MSFT would discover you have an unsupported configuration.
2) Single SAS JBOD is still a single point of failure as passive components still can fail. You need to deploy three SAS JBODs (make sure LSI controllers support SES) to have fully fault tolerant config. Pretty expensive... Google for "enclosure awareness". See:
"Enclosure Awareness Support - Tolerating an Entire Enclosure Failing
To support deployments that require an added level of fault tolerance, Storage Spaces supports associating each copy of data with a particular JBOD enclosure. This capability is known as enclosure awareness. With enclosure awareness, if one enclosure fails or goes offline, the data remains available in one or more alternate enclosures.
To use enclosure awareness with Storage Spaces, your environment must meet the following requirements:
JBOD storage enclosures must support SCSI Enclosure Services (SES).
Storage spaces must use the mirror resiliency type if you're using Windows Server 2012:
To tolerate one failed enclosure with two-way mirrors, you need three compatible storage enclosures. To tolerate two failed enclosures with three-way mirrors, you need five compatible storage enclosures."