Cell Metrics High value in FC_IO_BY_R_SKIP_SEC (High IO requests that bypass FlashCache) (Doc ID 1588941.1)

Last updated on JUNE 05, 2019

Applies to:

Symptoms

HDD disks are busy but flash are idle due to large reads issued by smart scans bypassing flash cache. This is shown as high values for FC_IO_BY_R_SKIP_SEC and compared low values for the others.

 [root@exadb01 ]# dcli -l root -g ~/cell_group cellcli -e "list metriccurrent where name like \'F.*IO.*BY.*SEC\'" |grep -v 0.0|grep _R_
exacel01: FC_IO_BY_R_MISS_SEC FLASHCACHE 1.746 MB/sec
exacel01: FC_IO_BY_R_SEC FLASHCACHE 2.106 MB/sec
exacel01: FC_IO_BY_R_SKIP_SEC FLASHCACHE 557 MB/sec
exacel02: FC_IO_BY_R_MISS_SEC FLASHCACHE 1.143 MB/sec
exacel02: FC_IO_BY_R_SEC FLASHCACHE 2.208 MB/sec
exacel02: FC_IO_BY_R_SKIP_SEC FLASHCACHE 580 MB/sec
exacel03: FC_IO_BY_R_MISS_SEC FLASHCACHE 1.330 MB/sec
exacel03: FC_IO_BY_R_SEC FLASHCACHE 2.223 MB/sec
exacel03: FC_IO_BY_R_SKIP_SEC FLASHCACHE 667 MB/sec
exacel04: FC_IO_BY_R_MISS_SEC FLASHCACHE 0.999 MB/sec
exacel04: FC_IO_BY_R_SEC FLASHCACHE 2.323 MB/sec
exacel04: FC_IO_BY_R_SKIP_SEC FLASHCACHE 560 MB/sec
exacel05: FC_IO_BY_R_MISS_SEC FLASHCACHE 0.958 MB/sec
exacel05: FC_IO_BY_R_SEC FLASHCACHE 2.228 MB/sec
exacel05: FC_IO_BY_R_SKIP_SEC FLASHCACHE 546 MB/sec
exacel06: FC_IO_BY_R_MISS_SEC FLASHCACHE 1.384 MB/sec
exacel06: FC_IO_BY_R_SEC FLASHCACHE 1.824 MB/sec
exacel06: FC_IO_BY_R_SKIP_SEC FLASHCACHE 620 MB/sec
exacel07: FC_IO_BY_R_MISS_SEC FLASHCACHE 1.964 MB/sec
exacel07: FC_IO_BY_R_SEC FLASHCACHE 2.581 MB/sec
exacel07: FC_IO_BY_R_SKIP_SEC FLASHCACHE 555 MB/sec

Cause