Write back flash cache exadata patching

Exadata flash cache enabled for write back during tests for an migration of a major customer application we saw in our awr reports that most of the jobs are very write intensive. Database architect,oracle rac dba,apps dba,sap,mysql,mongodb,postgressql administration with 12yrs of experience mongodb replica sets,sharding. The flash write capacity of a single full rack exadata database machine x42 exceeds 1,960,000. The exadata storage server comes with a substantial amount of flash storage.

Exadata smart flash cache overview write through and. From one db node using dcli check the currest status of the. Write caching eliminates disk bottlenecks in large scale oltp and batch workloads. Because the system was used in a 247 environment we had to implement the change in a rolling upgrade fashion. Why writethrough is still the default flash cache mode on. Installations,upgrades on all flavors of unix linux,solaris,hpaix. Smart flash cache logging redo logs are written to the disk and flash memory at th. Hi, i will explain smart flash cache feature of oracle exadata in this article. Smart flash cache in oracle exadata 2 it tutorials. With the announcement exadata x3, oracle has introduced a new feature called flashcache writeback to allow writes to cell flash cache aka exadata smart flashcache in writeback mode. Here are the concepts of exadata patching to make exadata. This was the point where we would like to test what happens when we change the flash cache mode from write through to write back.

Yes, this is wellknown and the process has been described in exadata writeback flash cache faq doc id 1500257. I had to enable the wbfc many times before and every time id restart the cell services, as note suggests. In the case of high redundancy this means a write of, say, 8kb will result in 3 copies of the 8kb block to be cached in exadata writeback cache in the flash cards of the cells that have the hdd backingstore for the blocks. With the write back flash cache feature, the exadata smart flash cache also caches database block writes.

Here are the concepts of exadata patching to make exadata dba life easy patching database is a common task for a remote dba, but when we talk about exadata patching it. Exadata software used to decide whether to cache these writes back into flashcache or not. In a recent tuning activity it was necessary to change the exadata smart flash cache from writethrough to writeback. Smart flash cache in oracle exadata 3 it tutorials. The exadata smart flash cache is a cache on the cell storage server for storing redodata until this data can be safely written to disk. Before jumping into the procedure itself, lets remind that the storage cells must run 11. Exadata flash cache enabled for write back stefans blog. Earlier with writethrough mode, writes were not written to flashcache, instead they were written directly to cell disks. Exadata smart flash cache overview write through and write back modes explained.