Re: Disk storage blob using more memory than expected.

[Peter Botha]

Showing percentages may hide the problem, especially if you have a large value configured for DataMemory in config.ini

I tried inserting only 1 record, and didn't see any extra memory used.
50 records shows the problem:

mysql> truncate table testblob;
Query OK, 0 rows affected (0.17 sec)

mysql> SELECT node_id, memory_type, used, CONCAT(ROUND(used/total * 100,1), '%') AS 'Percent used' FROM ndbinfo.memoryusage ORDER BY 2,1;
+---------+---------------------+---------+--------------+
| node_id | memory_type | used | Percent used |
+---------+---------------------+---------+--------------+
| 1 | Data memory | 1933312 | 0.2% |
| 2 | Data memory | 1933312 | 0.2% |
| 1 | Index memory | 180224 | 0.1% |
| 2 | Index memory | 180224 | 0.1% |
| 1 | Long message buffer | 262144 | 3.1% |
| 2 | Long message buffer | 262144 | 3.1% |
+---------+---------------------+---------+--------------+
6 rows in set (0.01 sec)

mysql> CALL GenerateFakeData(50, (1024*5)); # 5MB BLOB
Query OK, 1 row affected (0.04 sec)

mysql> SELECT node_id, memory_type, used, CONCAT(ROUND(used/total * 100,1), '%') AS 'Percent used' FROM ndbinfo.memoryusage ORDER BY 2,1;
+---------+---------------------+---------+--------------+
| node_id | memory_type | used | Percent used |
+---------+---------------------+---------+--------------+
| 1 | Data memory | 2195456 | 0.2% |
| 2 | Data memory | 2195456 | 0.2% |
| 1 | Index memory | 212992 | 0.1% |
| 2 | Index memory | 212992 | 0.1% |
| 1 | Long message buffer | 262144 | 3.1% |
| 2 | Long message buffer | 262144 | 3.1% |
+---------+---------------------+---------+--------------+
6 rows in set (0.00 sec)

mysql> truncate table testblob; CALL GenerateFakeData(50, (1024*500)); # 500MB BLOB
Query OK, 0 rows affected (0.14 sec)

Query OK, 1 row affected (0.51 sec)

mysql> SELECT node_id, memory_type, used, CONCAT(ROUND(used/total * 100,1), '%') AS 'Percent used' FROM ndbinfo.memoryusage ORDER BY 2,1;
+---------+---------------------+---------+--------------+
| node_id | memory_type | used | Percent used |
+---------+---------------------+---------+--------------+
| 1 | Data memory | 2228224 | 0.2% |
| 2 | Data memory | 2228224 | 0.2% |
| 1 | Index memory | 229376 | 0.1% |
| 2 | Index memory | 229376 | 0.1% |
| 1 | Long message buffer | 393216 | 4.7% |
| 2 | Long message buffer | 393216 | 4.7% |
+---------+---------------------+---------+--------------+
6 rows in set (0.01 sec)