Cold data is data that is rarely updated or accessed. You can use the cold data archiving feature to transfer this data to the low-cost Object Storage Service (OSS) to reduce your data storage costs.
How it works
PolarDB for MySQL supports archiving data in CSV or ORC format.
You can archive data manually or automatically. The archived data is converted to CSV or ORC format and stored as multiple files in OSS. This data is then automatically deleted from the PolarDB storage space, which reduces your storage fees. Nodes can then access the data in OSS over the Alibaba Cloud internal network. See Manually archive cold data and Automatically archive cold data.
The partitioned table archiving feature is currently in canary release. To use this feature, go to the Quota Center, find the quota by its Quota ID polardb_mysql_hybrid_partition, and click Apply in the Actions column.
Format comparison
Use the following comparison to select an appropriate format for archiving cold data.
Limitations apply when you archive standard tables, OSS external tables, and partitioned tables. Review these limitations carefully before you archive data to avoid impacting your business.
After cold data is archived, it is stored in a default system-provided Object Storage Service (OSS) bucket, not in your own OSS bucket. You can view the list of archived data only in the PolarDB console.
Partitioned table archiving methods:
Archive a partition: This method archives a partition of a table in place. The data remains in the original table, but the storage medium for that partition changes from PolarDB (hot storage) to OSS (cold storage). The table becomes a hybrid partitioned table containing both hot and cold partitions.
Archive a partition to an OSS external table: This method moves the data from a partition to a new, separate OSS external table. The original partition is then deleted from the source table.
Comparison item | CSV | ORC |
Open-source format | Yes | Yes |
Archiving method |
| Manual archiving: |
Archiving speed | Fast Note Only single-threaded archiving is supported. | Slow Note Only single-threaded archiving is supported. |
Query speed |
Note Both single-threaded and multi-threaded data reads are supported. |
Note Only single-threaded data reads are supported. |
Transaction support | No | No |
Indexing capability | No | No |
How to modify archived data | Archived tables in OSS are read-only. To modify the data, you must import it back to the PolarDB storage space. | |
Storage space usage | Same as the storage space used by a table in the InnoDB engine without an index. | For the same amount of data, ORC format uses 45% of the storage space required by CSV format. |
Backup and recovery | Not supported. Note The backup operation does not back up archived cold data in OSS. Therefore, you cannot use backups to recover databases or tables, restore from backups, or perform a point-in-time recovery. | |
Impact after archiving |
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Scope
Archiving to CSV format
For Cluster Edition clusters, one of the following kernel versions is required:
MySQL 8.0.1 revision 8.0.1.1.47 or later.
MySQL 8.0.2 revision 8.0.2.2.10 or later.
For Multi-master Cluster (Limitless) Edition clusters, kernel version 8.0.1.0.13 or later is required.
Archiving to ORC format
For Cluster Edition clusters, revision version 8.0.2.2.30 or later is required.
For Multi-master Cluster (Limitless) Edition clusters, revision version 8.0.2.2.30 or later is required.
Billing
Cold data is billed based on the storage capacity used in OSS. You can purchase a PolarDB storage plan to offset the storage costs of cold data in OSS. For more information, see Storage plans.
Regions in the Chinese mainland | China (Hong Kong) and regions outside China |
USD 0.0000325 per GB-hour | USD 0.0000455 per GB-hour |
Example: You enable and perform cold data archiving for a cluster deployed in the Chinese mainland. The amount of cold data archived in OSS is 100 GB. The hourly cold data storage fee is 100 GB × USD 0.0000325 per GB-hour = USD 0.00325 per hour.
For information about how to view the amount of archived cold data, see View information about the cold data archived in OSS.
How to use
For more information, see Usage instructions.