Syneto products have a built-in mechanism for protecting against silent data corruption. Silent data corruption means that data being read is different from the data previously written to a drive. There are several ways this could happen, from controller firmware errors all the way to natural events like cosmic radiation.
To prevent silent data corruption, all data blocks are written accompanied by a checksum which uniquely identifies them. Later, when reading the data, its contents are cross-checked against the checksum and if they don’t match, the original version of the data can be reconstructed. This process is called self-healing and happens behind the scenes as blocks are being read into memory.
Self-healing protects especially hot data, which is accessed frequently and thus checked frequently for its consistency/integrity. Less frequently accessed (cold) data is at a larger risk because its blocks may accumulate multiple errors, which could render checksums useless. To protect cold data, the system can be configured to periodically run a scan of the drives and fix corruptions. This process can also be initiated manually.
To start a manual integrity check or to schedule one, use the drop-down on the desired disk pool and select Check integrity. This will allow to start/stop an integrity check or to enable/disable periodical integrity checks. The periodical checks will run every 1/2/3/4 weeks at 23:00 on Friday evening.
Configure integrity checking speed
Integrity checks execute as fast as the drives allow, but their I/O priority remains below that of normal reads/writes. This operation might negatively impact overall performance, though the disk pool’s data will remain usable while the integrity checks run.
Because the integrity check operation might negatively impact performance, the speed at which the data is traversed can be changed. Slow integrity check will take a longer time to run but will have a small impact on performance. Fast integrity check will take less time to run, but it may have a bigger impact on performance.