Balancing database workloads through migration

1. A method for balancing database workloads among a plurality of database servers, the method comprising:

when a new server is available, selecting a set of master and slave databases to be migrated to the new server and migrating the selected databases to result in a balanced new workload among all servers while minimizing migration cost;

during operation, if a workload unbalance is detected in real-time from a workload change, iteratively selecting one database at a time to migrate to a different server to balance the workload; and

determining a metric for a given database configuration including a mean and a variance, wherein the variance is determined as:

σ 2 =c mem ·σ memCap 2 +c cpu σ cpuCap ,

where c mem and c cpu are parameters for calibrating different units between memory and a CPU.

2. The method of claim 1 , comprising applying a metric to measure a goodness of a given database configuration.

3. The method of claim 2 , wherein the metric comprises system resources including processor (CPU) usage and memory usage.

4. The method of claim 2 , wherein the metric comprises different factors in a unified way through a weighting strategy and a vector norm.

5. The method of claim 1 , wherein the selecting a set of master databases and slave databases for migration further comprises considering one or more factors including (a) the expect cost reduction after the migration, (b) the master-to-slave ratio at each of the server after migration, and (c) the migration cost that is related to the size of each database.

6. The method of claim 1 , comprising choosing an optimal order of migration to minimize impact on the system during migration.

7. The method of claim 1 , comprising iteratively selecting a next database to migrate and a corresponding target database server to eliminate a hot spot.

8. The method of claim 1 , comprising iteratively migrating one database at a time until all hot spots are eliminated.

9. The method of claim 1 , comprising setting

c

mem

=

1

μ

memCap

2

⁢

⁢

and

⁢

⁢

c

cpu

=

1

μ

cpuCap

2

.

10. A system for balancing database workloads among a plurality of database servers, the system comprising:

a processor;

code executable by the processor when a new server is available, including instructions for selecting a set of master and slave databases to be migrated to the new server; and migrating the selected databases to result in a balanced new workload among all servers while minimizing migration cost; and

code executable by the processor during operation, including instructions for detecting if workload unbalance is detected in real time and iteratively selecting one database at a time to migrate to a different server to balance the workload; and

code for determining a metric for a given database configuration including a mean and a variance, wherein the variance is determined as:

σ 2 =c mem ·σ memCap 2 +c cpu ·σ cpuCap 2 ,

where c mem and c cpu are parameters for calibrating different units between memory and a CPU.

11. The system of claim 10 , comprising code for applying a metric to measure a goodness of a given database configuration.

12. The system of claim 11 , wherein the metric comprises system resources including processor (CPU) usage and memory usage.

13. The system of claim 10 , wherein the metric combines different factors in a unified way through a weighting strategy and a vector norm.

14. The system of claim 10 , wherein the code for selecting a set of master databases and slave databases for migration further comprises considering one or more factors including (a) the expect cost reduction after the migration, (b) the master-to-slave ratio at each of the server after migration, and (c) the migration cost that is related to the size of each database.

15. The system of claim 10 , comprising code for choosing an optimal order of migration to minimize impact on the system during migration.

16. The system of claim 10 , comprising code for iteratively selecting a next database to migrate and a corresponding target database server to eliminate a hot spot.

17. The system of claim 10 , comprising code for iteratively migrating one database at a time until all hot spots are eliminated.

18. The system of claim 10 , comprising code for setting

c

mem

=

1

μ

memCap

2

⁢

⁢

and

⁢

⁢

c

cpu

=

1

μ

cpuCap

2

.