choose default values upon incorrect storage_class value (#16058)

internal/config/storageclass/storage-class.go

@@ -304,7 +304,12 @@ func LookupConfig(kvs config.KVS, setDriveCount int) (cfg Config, err error) {
 	// Validation is done after parsing both the storage classes. This is needed because we need one
 	// storage class value to deduce the correct value of the other storage class.
 	if err = validateParity(cfg.Standard.Parity, cfg.RRS.Parity, setDriveCount); err != nil {
-		return Config{}, err
+		cfg.RRS.Parity = defaultRRSParity
+		if setDriveCount == 1 {
+			cfg.RRS.Parity = 0
+		}
+		cfg.Standard.Parity = DefaultParityBlocks(setDriveCount)
+		return cfg, err
 	}
 
 	return cfg, nil