> Almost all big data storage solutions are NoSQL.
Most I've seen aren't. NoSQL means non-relational database. Most big data solutions I've seen will not use a database at all. An example is hadoop.
Once you have a database, SQL makes a lot of sense. There are big data SQL solutions, mostly in the form of columnar read-optimized databases.
On the above, a little bit of relational can make a huge performance difference, in the form of, for example, a big table with compact data with indexes into small data tables. That can be algorithmically a lot more performant than the same thing without relations.
Most I've seen aren't. NoSQL means non-relational database. Most big data solutions I've seen will not use a database at all. An example is hadoop.
Once you have a database, SQL makes a lot of sense. There are big data SQL solutions, mostly in the form of columnar read-optimized databases.
On the above, a little bit of relational can make a huge performance difference, in the form of, for example, a big table with compact data with indexes into small data tables. That can be algorithmically a lot more performant than the same thing without relations.