Storage block balancing using volume part migration

1. A method, comprising:

obtaining, by at least one entity of a metadata manager on at least one server node of a storage system, a capacity utilization of a plurality of storage blocks each storing at least a portion of one or more storage volumes, wherein the capacity utilization of a given storage block of the plurality of storage blocks is based at least in part on an amount of storage of the given storage block that is storing the at least the portion of the one or more storage volumes stored by the given storage block and corresponding snapshots of the at least the portion of the one or more storage volumes stored by the given storage block, wherein the storage system further comprises one or more storage nodes separate from the at least one server node, wherein the storage nodes comprise a plurality of storage devices, and wherein the plurality of storage devices comprise the plurality of storage blocks; and

in response to the capacity utilization of the given storage block being above an upper target threshold, migrating, by the at least one entity of the metadata manager on the server node, a volume part of the given storage block of at least one storage node to a different storage block of at least one different storage node, wherein the different storage block has a capacity utilization below a lower target threshold and is within a same storage pool as the given storage block, wherein the different storage block is selected based at least in part on an evaluation of a relative capacity utilization among the storage blocks, of the at least one different storage node, that have a capacity utilization that is below the lower target threshold, and wherein the volume part comprises a subset of a storage volume, wherein the at least one entity of the metadata manager is configured to: (i) migrate the volume part of the given storage block to the different storage block within the same storage pool; and (ii) migrate one or more different volume parts to one or more target storage blocks of a different storage pool, wherein the capacity utilization of the given storage block is above the upper target threshold;

wherein the method is performed by at least one processing device comprising a processor coupled to a memory.

2. The method of claim 1 , further comprising creating a new storage block in response to no storage block being below the lower target threshold.

3. The method of claim 1 , wherein the given storage block has a highest capacity utilization among a plurality of storage blocks.

4. The method of claim 1 , wherein the different storage block below the lower target threshold has a highest capacity utilization, among the storage blocks of the at least one different storage node, that is below the lower target threshold.

5. The method of claim 1 , further comprising migrating a volume part from a first storage block to a second storage block in response to one or more of: (i) a number of blocks exceeding a first threshold; (ii) a plurality of volume parts of the first storage block fitting in one or more additional storage blocks in the same storage pool that are below the lower target threshold; and (iii) a storage block having a lowest utilization in the storage pool being smaller than a second threshold.

6. The method of claim 1 , further comprising migrating a volume part from a first storage block to a second storage block and wherein the first storage block has a lowest capacity utilization among the plurality of storage blocks and wherein the second storage block has a highest capacity utilization among the plurality of storage blocks below the lower target threshold.

7. The method of claim 1 , further comprising migrating a volume part from a first storage block to a second storage block in response to a storage block having a lowest utilization in the storage pool being smaller than a second threshold and wherein the second threshold is set to: a first value when a number of blocks in a storage system comprising the plurality of storage blocks is below a third threshold, a second value when the number of blocks is above a fourth threshold, and a third value based on a linear expression when the number of blocks is between the third and fourth thresholds.

8. The method of claim 1 , further comprising migrating a volume part from a first storage block to a second storage block and reclaiming the given storage block in response to the given storage block being empty after the migration.

9. An apparatus comprising:

at least one processing device comprising a processor coupled to a memory;

the at least one processing device being configured to implement the following steps:

obtaining, by at least one entity of a metadata manager on at least one server node of a storage system, a capacity utilization of a plurality of storage blocks each storing at least a portion of one or more storage volumes, wherein the capacity utilization of a given storage block of the plurality of storage blocks is based at least in part on an amount of storage of the given storage block that is storing the at least the portion of the one or more storage volumes stored by the given storage block and corresponding snapshots of the at least the portion of the one or more storage volumes stored by the given storage block, wherein the storage system further comprises one or more storage nodes separate from the at least one server node, wherein the storage nodes comprise a plurality of storage devices, and wherein the plurality of storage devices comprise the plurality of storage blocks; and

in response to the capacity utilization of the given storage block being above an upper target threshold, migrating, by the at least one entity of the metadata manager on the server node, a volume part of the given storage block of at least one storage node to a different storage block of at least one different storage node, wherein the different storage block has a capacity utilization below a lower target threshold and is within a same storage pool as the given storage block, wherein the different storage block is selected based at least in part on an evaluation of a relative capacity utilization among the storage blocks, of the at least one different storage node, that have a capacity utilization that is below the lower target threshold, and wherein the volume part comprises a subset of a storage volume, wherein the at least one entity of the metadata manager is configured to: (i) migrate the volume part of the given storage block to the different storage block within the same storage pool; and (ii) migrate one or more different volume parts to one or more target storage blocks of a different storage pool, wherein the capacity utilization of the given storage block is above the upper target threshold.

10. The apparatus of claim 9 , further comprising migrating a volume part from a first storage block to a second storage block in response to one or more of: (i) a number of blocks exceeding a first threshold; (ii) a plurality of volume parts of the first storage block fitting in one or more additional storage blocks in the same storage pool that are below the lower target threshold; and (iii) a storage block having a lowest utilization in the storage pool being smaller than a second threshold.

11. The apparatus of claim 9 , further comprising migrating a volume part from a first storage block to a second storage block and wherein the first storage block has a lowest capacity utilization among the plurality of storage blocks and wherein the second storage block has a highest capacity utilization among the plurality of storage blocks below the lower target threshold.

12. The apparatus of claim 9 , further comprising migrating a volume part from a first storage block to a second storage block in response to a storage block having a lowest utilization in the storage pool being smaller than a second threshold and wherein the second threshold is set to: a first value when a number of blocks in a storage system comprising the plurality of storage blocks is below a third threshold, a second value when the number of blocks is above a fourth threshold, and a third value based on a linear expression when the number of blocks is between the third and fourth thresholds.

13. The apparatus of claim 9 , further comprising migrating a volume part from a first storage block to a second storage block and reclaiming the given storage block in response to the given storage block being empty after the migration.

14. The apparatus of claim 9 , further comprising creating a new storage block in response to no storage block being below the lower target threshold.

15. The apparatus of claim 9 , wherein the given storage block has a highest capacity utilization among a plurality of storage blocks.

16. The apparatus of claim 9 , wherein the different storage block below the lower target threshold has a highest capacity utilization, among the storage blocks of the at least one different storage node, that is below the lower target threshold.

17. A non-transitory processor-readable storage medium having stored therein program code of one or more software programs, wherein the program code when executed by at least one processing device causes the at least one processing device to perform the following steps:

obtaining, by at least one entity of a metadata manager on at least one server node of a storage system, a capacity utilization of a plurality of storage blocks each storing at least a portion of one or more storage volumes, wherein the capacity utilization of a given storage block of the plurality of storage blocks is based at least in part on an amount of storage of the given storage block that is storing the at least the portion of the one or more storage volumes stored by the given storage block and corresponding snapshots of the at least the portion of the one or more storage volumes stored by the given storage block, wherein the storage system further comprises one or more storage nodes separate from the at least one server node, wherein the storage nodes comprise a plurality of storage devices, and wherein the plurality of storage devices comprise the plurality of storage blocks; and

in response to the capacity utilization of the given storage block being above an upper target threshold, migrating, by the at least one entity of the metadata manager on the server node, a volume part of the given storage block of at least one storage node to a different storage block of at least one different storage node, wherein the different storage block has a capacity utilization below a lower target threshold and is within a same storage pool as the given storage block, wherein the different storage block is selected based at least in part on an evaluation of a relative capacity utilization among the storage blocks, of the at least one different storage node, that have a capacity utilization that is below the lower target threshold, and wherein the volume part comprises a subset of a storage volume, wherein the at least one entity of the metadata manager is configured to: (i) migrate the volume part of the given storage block to the different storage block within the same storage pool; and (ii) migrate one or more different volume parts to one or more target storage blocks of a different storage pool, wherein the capacity utilization of the given storage block is above the upper target threshold.

18. The non-transitory processor-readable storage medium of claim 17 , further comprising migrating a volume part from a first storage block to a second storage block in response to one or more of: (i) a number of blocks exceeding a first threshold; (ii) a plurality of volume parts of the first storage block fitting in one or more additional storage blocks in the same storage pool that are below the lower target threshold; and (iii) a storage block having a lowest utilization in the storage pool being smaller than a second threshold.

19. The non-transitory processor-readable storage medium of claim 17 , further comprising migrating a volume part from a first storage block to a second storage block in response to a storage block having a lowest utilization in the storage pool being smaller than a second threshold and wherein the second threshold is set to: a first value when a number of blocks in a storage system comprising the plurality of storage blocks is below a third threshold, a second value when the number of blocks is above a fourth threshold, and a third value based on a linear expression when the number of blocks is between the third and fourth thresholds.

20. The non-transitory processor-readable storage medium of claim 17 , further comprising migrating a volume part from a first storage block to a second storage block and reclaiming the given storage block in response to the given storage block being empty after the migration.