SATA stands for Serial Advanced Technology Attachment and SAS stands for Serial Attached SCSI (SCSI Stands for Small Computer System Interface, typically pronounced as “scuzzy”). They’re two types of interface used for transferring data to and from hard drives. In layman’s terms they are connectors that connect the server motherboard with the hard drives.
In terms of capacity though, SATA drives win hands down.
3TB SATA hard drives are not uncommon and there are 8TB disk offerings in a 3.5 inch format.
Generally though they are most cost effective in the 1TB to 3TB range.
SAS drives on the other hand tend to max at around 900GB although the most popular configuration is around 450GB to 500GB.