7.7.1.4 ALTER FLASHCACHE

Purpose

The ALTER FLASHCACHE command stops new data from being cached on the flash cache and then flushes data not synchronized with the grid disks (dirty data) from flash cache to the specified disks.

Syntax

ALTER FLASHCACHE { ALL [size=fc_size] | CELLDISK="cdisk1 [,cdisk2] ..." [, size=fc_size] [FORCE] }
      { FLUSH [NOWAIT] | CANCEL FLUSH }

Usage Notes

Note:

The FLUSH option stops new data from being cached on the flash cache until CELLSRV restarts, or the flush operation is canceled with the ALTER FLASHCACHE CANCEL FLUSH command.

  • The ALL option affects all available flash cell disks.

  • The CELLDISK option allows specific cell disks to be flushed.

  • The FORCE option allows you to forcefully change the set of cell disks used by the flash cache.

  • If specified, the size attribute re-sizes the flash cache. The value is validated.

    If a valid size is specified in conjunction with the ALL option, then the flash cache is dropped and re-created on all of the cell disks using the specified size.

    If a valid size is specified in conjunction with the CELLDISK option, then the flash cache is dropped and re-created on the specified cell disks using the specified size.

  • The FLUSH option synchronizes dirty data from the flash cache to the grid disks. Dirty data is data that has not been synchronized with the grid disk. Synchronization of dirty data can be a lengthy process, depending on the number of bytes to be synchronized. Use the following command to check the progress: 

    LIST CELLDISK ATTRIBUTES name, flushstatus, flusherror

  • The ALTER FLASHCACHE CELLDISK= ... FLUSH command does not flush the dirty data when the data cannot be read from the flash cache or written to disk. To flush the dirty data from the flash disk to grid disks use the ALTER GRIDDISK ... FLUSH command.

  • The ALTER FLASHCACHE ... FLUSH command stops new data from being written to the flash cache and then synchronizes all data in the flash cache with the hard disks. As a result, all data is removed from the flash cache. When the flash cache is re-enabled, the flash cache activity metrics are reset.

  • The CANCEL FLUSH option terminates an earlier flush operation, and reinstates flash caching.

  • The NOWAIT option allows the ALTER command to complete while the flush operation is in progress.

  • By default, 5 percent of space on Extreme Flash storage servers is used for write-back flash cache.

Example 7-35 Flushing Dirty Blocks from Flash Cell Disks

This example shows how to flush dirty blocks from all flash cell disks.

CellCLI> ALTER FLASHCACHE ALL FLUSH
Flash cache on FD_00_scac01cel07 successfully altered
Flash cache on FD_01_scac01cel07 successfully altered
Flash cache on FD_02_scac01cel07 successfully altered
...
Flash cache on FD_14_scac01cel07 successfully altered
Flash cache on FD_15_scac01cel07 successfully altered

Parent topic: ALTER