Data integrity

As part of maintaining data integrity, Ceph provides numerous mechanisms to guard against bad disk sectors and bit rot.

Scrubbing

Ceph OSD Daemons can scrub objects within placement groups. That is, Ceph OSD Daemons can compare object metadata in one placement group with its replicas in placement groups stored on other OSDs. Scrubbing usually performed daily catches bugs or storage errors. Ceph OSD Daemons also perform deeper scrubbing by comparing data in objects bit-for-bit. Deep scrubbing usually performed weekly finds bad sectors on a drive that weren’t apparent in a light scrub.

CRC Checks

When using BlueStore, Ceph can ensure data integrity by conducting a cyclical redundancy check (CRC) on write operations; then, store the CRC value in the block database. On read operations, Ceph can retrieve the CRC value from the block database and compare it with the generated CRC of the retrieved data to ensure data integrity instantly.