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

Last updated on OCTOBER 24, 2013

Applies to:

Oracle Exadata Storage Server Software - Version 11.2.3.2.1 and later
Information in this document applies to any platform.

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@dm01db01 rudi]# dcli -l root -g ~/cell_group cellcli -e "list metriccurrent where name like \'F.*IO.*BY.*SEC\'" |grep -v 0.0|grep _R_
dm03cel01: FC_IO_BY_R_MISS_SEC FLASHCACHE 1.746 MB/sec
dm03cel01: FC_IO_BY_R_SEC FLASHCACHE 2.106 MB/sec
dm03cel01: FC_IO_BY_R_SKIP_SEC FLASHCACHE 557 MB/sec
dm03cel02: FC_IO_BY_R_MISS_SEC FLASHCACHE 1.143 MB/sec
dm03cel02: FC_IO_BY_R_SEC FLASHCACHE 2.208 MB/sec
dm03cel02: FC_IO_BY_R_SKIP_SEC FLASHCACHE 580 MB/sec
dm03cel03: FC_IO_BY_R_MISS_SEC FLASHCACHE 1.330 MB/sec
dm03cel03: FC_IO_BY_R_SEC FLASHCACHE 2.223 MB/sec
dm03cel03: FC_IO_BY_R_SKIP_SEC FLASHCACHE 667 MB/sec
dm03cel04: FC_IO_BY_R_MISS_SEC FLASHCACHE 0.999 MB/sec
dm03cel04: FC_IO_BY_R_SEC FLASHCACHE 2.323 MB/sec
dm03cel04: FC_IO_BY_R_SKIP_SEC FLASHCACHE 560 MB/sec
dm03cel05: FC_IO_BY_R_MISS_SEC FLASHCACHE 0.958 MB/sec
dm03cel05: FC_IO_BY_R_SEC FLASHCACHE 2.228 MB/sec
dm03cel05: FC_IO_BY_R_SKIP_SEC FLASHCACHE 546 MB/sec
dm03cel06: FC_IO_BY_R_MISS_SEC FLASHCACHE 1.384 MB/sec
dm03cel06: FC_IO_BY_R_SEC FLASHCACHE 1.824 MB/sec
dm03cel06: FC_IO_BY_R_SKIP_SEC FLASHCACHE 620 MB/sec
dm03cel07: FC_IO_BY_R_MISS_SEC FLASHCACHE 1.964 MB/sec
dm03cel07: FC_IO_BY_R_SEC FLASHCACHE 2.581 MB/sec
dm03cel07: FC_IO_BY_R_SKIP_SEC FLASHCACHE 555 MB/sec

Cause

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