This topic describes the reliability and consistency of Cloud Storage Gateway (CSG).
- In the cache mode, data is written to a disk by using synchronous I/O to prevent data loss due to power failures.
- CSG ensures the durability and reliability of data in the local cache disks by using Alibaba Cloud disks.
- On-premises gateways depend on the reliability of the backend storage in your virtual environment. We recommend that you use Redundant Array of Independent Disks (RAID) storage or a distributed storage system as local cache disks.
- CSG refreshes and uploads data in the local cache disks to an OSS bucket. Alibaba Cloud OSS guarantees 99.9999999999% reliability. This ensures data security and reliability when you transfer data from the gateway to Alibaba Cloud.
- A 64-bit cyclic redundancy check (CRC-64) is implemented on the data that is uploaded to an OSS bucket from the gateway. If you send data from your data center to an OSS bucket, a checksum is generated and sent along with the data. Another checksum is generated by OSS and compared with the checksum that is received by OSS. If the two are equal, the uploading process is complete.
- If you upload a small file to an OSS bucket, the file gateway generates a checksum of the file. If you upload a large file in multiple parts to an OSS bucket, the file gateway implements CRC-64 on each part. This ensures consistency between the two checksums that are generated in your data center and the OSS bucket.
- A block gateway splits iSCSI volumes into storage allocation units. If you upload data in multiple units to an OSS bucket, the block gateway implements CRC-64 on the data in each unit. This ensures that the persistent data in the cloud is consistent with the data you write.