Sizing Memory-Optimized Workloads

Prashanth Purnananda gives us a few notes regarding memory-optimized table sizes:

Recovering database with memory-optimized tables involves hydrating the contents of checkpoint files (data/delta files) into memory and then replaying the tail of the log (see this link for more details). One of the important difference between disk based tables and memory-optimized store is frequency of checkpoints. Automatic checkpointing for in-memory tables occurs every 1.5GB of log records unlike traditional or indirect checkpoints (where checkpointing is done more often) leading to longer tail of log for in-memory tables. The 1.5 GB log flush is chosen to strike the right balance between flooding the IO subsystem with too many small inefficient IO operations and too few large IOPs. In most scenarios observed by our CSS teams, long recovery times for memory optimized databases is caused by the long tail of log which needs to be recovered for in-memory tables in the database. For these scenarios, running a manual checkpoint before a restart can reduce recovery times as manual checkpoint forces the checkpoint for memory optimized tables in addition to disk based tables.

If you’re looking at creating memory-optimized tables, these are important administrative notes.

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