The WT_SESSION.create method defaults to checksum=uncompressed. This configuration turns off checksums when blocks are also compressed. Choosing uncompressed as the default was based on the belief that compression engines would generally support strong checksums and so separate checksums would not be necessary. This has proven not to be the case, and none of the standard compression engines in WiredTiger (lz4, snappy, zlib and zstd), have strong enough checksum support that separate checksums are not required. To prevent application errors, the default checksum configuration should be checksum=on.

Although compression engines generally do not include strong checksum support. encryption engines do include strong checksum support. Add a new checksum configuration, checksum=unencrypted, to support turning off checksums when encryption engines that support strong checksums are configured and the blocks are encrypted.