Got error 28 from storage engine

in query:
SELECT productID, name, Price, price_call, price_members, special_sale, brief_description, slug FROM SKH_products where categoryID=32 AND productID!=724 ORDER BY RAND() LIMIT 5
Warning : Unknown: write failed: No space left on device (28) in unknown
Warning : Unknown: Failed to write session data (files). Please verify that the current setting of session.save_path is correct () in unknown