Exadata · Oracle

Flashcache on Exadata Cell Notes

How much flashcache is used ?

CellCLI> list metriccurrent FC_BY_USED,FC_BYKEEP_USED,FC_BY_DIRTY
FC_BY_USED FLASHCACHE 299 MB
FC_BYKEEP_USED FLASHCACHE 0.000 MB
FC_BY_DIRTY FLASHCACHE 19.602 MB

OR

[root@hst1celnod01 ~]# dcli -g cell_group -l root cellcli -e "list metriccurrent FC_BY_USED,FC_BYKEEP_USED,FC_BY_DIRTY "
hst1celnod01: FC_BY_USED FLASHCACHE 538,274 MB
hst1celnod01: FC_BYKEEP_USED FLASHCACHE 0.000 MB
hst1celnod01: FC_BY_DIRTY FLASHCACHE 131,038 MB
hst1celnod02: FC_BY_USED FLASHCACHE 1,421,336 MB
hst1celnod02: FC_BYKEEP_USED FLASHCACHE 0.000 MB
hst1celnod02: FC_BY_DIRTY FLASHCACHE 1,011,465 MB
hst1celnod03: FC_BY_USED FLASHCACHE 1,422,147 MB
hst1celnod03: FC_BYKEEP_USED FLASHCACHE 0.000 MB
hst1celnod03: FC_BY_DIRTY FLASHCACHE 1,010,438 MB
hst1celnod04: FC_BY_USED FLASHCACHE 1,421,314 MB
hst1celnod04: FC_BYKEEP_USED FLASHCACHE 0.000 MB
hst1celnod04: FC_BY_DIRTY FLASHCACHE 1,012,997 MB
hst1celnod05: FC_BY_USED FLASHCACHE 1,421,279 MB
hst1celnod05: FC_BYKEEP_USED FLASHCACHE 0.000 MB
hst1celnod05: FC_BY_DIRTY FLASHCACHE 1,012,152 MB
hst1celnod06: FC_BY_USED FLASHCACHE 1,421,217 MB
hst1celnod06: FC_BYKEEP_USED FLASHCACHE 0.000 MB
hst1celnod06: FC_BY_DIRTY FLASHCACHE 1,010,493 MB
hst1celnod07: FC_BY_USED FLASHCACHE 1,422,550 MB
hst1celnod07: FC_BYKEEP_USED FLASHCACHE 0.000 MB
hst1celnod07: FC_BY_DIRTY FLASHCACHE 1,013,468 MB

Flashcache Mode

FlashCache mode could be WriteThrough or WriteBack.You can check the writeback mode like this

CellCLI> list cell attributes flashCacheMode detail

Drop Flashcache

If you are using WriteBack flashcache then you need to first flush the flashcache.
If it is WriteThrough you will get an error when you flush the flashcahe. Error is like this : “Flash cache flush on FD_00_hst1celnod01 failed because flashcache is not in the correct status to perform flush operations.”

CellCLI> alter flashcache all flush
CellCLI> drop flashcache
CellCLI> drop flashlog
CellCLI> drop celldisk all flashdisk

Create Flashcache

On exadata you can create flashcache using the following commands.

CellCLI> create celldisk all flashdisk
CellCLI> create flashlog all

Then create the flashcache.
This command uses all the available flash disks (FDOMs)

CellCLI> create flashcache all

OR

you can create the flash cache only using a part of the flash disks.

CellCLI> create flashcache celldisk='FD_04_hst1celnod01,FD_07_hst1celnod01,FD_05_hst1celnod01,FD_01_hst1celnod01,FD_06_hst1celnod01,FD_03_hst1celnod01,FD_02_hst1celnod01,FD_00_hst1celnod01'
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