Hi, using FLASH_SSD_OPTIMIZED already sets the number of threads to 4. This optimization can improve the source throughput and reduce the delayed wrate rate.
If this optimization didn't fix the back pressure, could you share more information about your job? Could you check the metric of the back pressured operator, e.g. check if it is caused by write-heavy or read-heavy tasks? You could try tuning rocksdb.writebuffer for write-heavy tasks. On Thu, Jul 21, 2022 at 5:59 PM Yaroslav Tkachenko <yaros...@goldsky.io> wrote: > Hi! > > I'd try re-running the SSD test with the following config options: > > state.backend.rocksdb.thread.num: 4 > state.backend.rocksdb.predefined-options: FLASH_SSD_OPTIMIZED > > > On Thu, Jul 21, 2022 at 4:11 AM vtygoss <vtyg...@126.com> wrote: > >> Hi, community! >> >> >> I am doing some performance tests based on my scene. >> >> >> 1. Environment >> >> - Flink: 1.13.5 >> >> - StateBackend: RocksDB, incremental >> >> - user case: complex sql contains 7 joins and 2 aggregation, input data >> 30,000,000 records and output 60,000,000 records about 80GB. >> >> - resource: flink on yarn. JM 2G, one TM 24G(8G on-heap, 16G off-heap). 3 >> slots per TM >> >> - only difference: different config 'state.backend.rocksdb.localdir', one >> SATA disk or one SSD disk. >> >> >> 2. rand write performance difference between SATA and SSD >> >> 4.8M/s is archived using SATA, while 48.2M/s using SSD. >> >> ``` >> >> fio -direct=1 -iodepth 64 -thread -rw=randwrite -ioengine=sync >> -fsync=1 -runtime=300 -group_reporting -name=xxx -size=100G >> --allow_mounted_write=1 -bs=8k -numjobs=64 -filename=/mnt/disk11/xx >> >> ``` >> >> >> 3. In my use case, Flink SQL application finished in 41minutes using >> SATA, while 45minutes using SSD. >> >> >> Does this comparision suggest that the way to improve RocksDB performance >> by using SSD is not effective? >> >> The direct downstream of the BackPressure operator is HdfsSink, does that >> mean the best target to improve application performance is HDFS? >> >> >> Thanks for your any replies or suggestions. >> >> >> Best Regards! >> >> >> >> >> >> >> >> >>
