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Hybrid Transactional and Analytical Processing (HTAP) systems
suffer from workload interference at the software and hardware
level. We examine workload interference for HTAP systems and
highlight investigation directions to mitigate the interference.
We use the popular two-copy HTAP architecture. The OLTP and
OLAP sides are independent components with their own private
copies of the data. The OLTP side is a row-store, whereas the OLAP
side is a column-store. The OLTP and OLAP sides are connected
by means of an intermediate data structure, delta, that keeps track
of the fresh tuples that are generated by the OLTP side, but not
yet transferred to the OLAP side. OLTP transactions register their
modifications to delta before committing. OLAP queries first prop-
agate fresh tuples from the OLTP side to the OLAP side and then
perform query execution over the data at the OLAP side.
HTAP systems suffer from interference at both the
software and hardware level. Software-level interference depends
on the OLTP and fresh tuple propagation throughput. In order
to minimize interference, HTAP systems should ensure that fresh
tuple propagation throughput is greater than the throughput of the
OLTP transactions that generate the fresh tuples.
Hardware-level interference depends on the demand for shared
resources such as LLC and memory bandwidth by the OLTP and
OLAP workloads. HTAP systems should isolate the OLTP and OLAP
workloads in the shared resources and use micro-architectural re-
source allocation policies that assign the optimal amount of re-
sources to OLTP and OLAP workloads to minimize hardware-level
interference.
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