Sunday, March 20, 2011

What should we contain Online Redo Log Files in Flash Disk?

I asked about How to use Flash Disk (Exadata)? on oracle-l - I think this may have benefit for someone. However, We should know about Flash Disk benefits on Oracle Database. and I have some question: What should we contain Online Redo Log Files in Flash Disk?

Online redo log files record all changes made to Oracle Database data files and control file. When a change is made to the database, Oracle Database generates a redo record in the redo buffer. Log Writer (LGWR) writes the contents of the redo buffer to the online redo log. LGWR performs sequential writes of redo to disk.

That's a concept what we know, and LGWR can perform fast sequential writes of redo to disk, the database improves performance.

A solid-state drive (SSD)
is a data storage device that uses solid-state memory to store persistent data with the intention of providing access in the same manner of a traditional block i/o hard disk drive. SSD has write speeds lower than its read speeds and sequential writes isn't better faster than Hard Disk.

So, I think It's not good idea to contain Online Redo Log Files in Flash Disk. How do you think?

Reference:
http://www.freelists.org/post/oracle-l/How-do-you-use-FlashDisk
http://www.emc.com/collateral/hardware/white-papers/h5967-leveraging-clariion-cx4-oracle-deploy-wp.pdf

3 comments:

Gary Myers said...

Guy Harrison had some info on this.
http://guyharrison.squarespace.com/blog/2010/10/21/accelerating-oracle-database-performance-with-ssd.html

He came to the same conclusion, that the write penalty meant there probably wouldn't be a benefit.

Surachart said...

@Gary
thank you so much

hmartinezlopez said...

they serve only to read, represent a difference of 200 to 10000 (aprox) with FC disks, making them ideal for flash "keep" cache...