Re: Advice configuring ServeRAID 8k for performance

[Greg Smith <greg@xxxxxxxxxxxxxxx>]

Bruce Momjian wrote:

Scott Carey wrote:
  

Don't ever have WAL and data on the same OS volume as ext3.

...
One partition for WAL, one for data.  If using ext3 this is essentially
a performance requirement no matter how your array is set up underneath.
    

Do we need to document this?
  

Not for 9.0.  What Scott is suggesting is often the case, but not always; I can produce a counter example at will now that I know exactly which closets have the skeletons in them.  The underlying situation is more complicated due to some limitations to the whole "spread checkpoint" code that is turning really sour on newer hardware with large amounts of RAM.  I have about 5 pages of written notes on this specific issue so far, and that keeps growing every week.  That's all leading toward a proposed 9.1 change to the specific fsync behavior.  And I expect to dump a large stack of documentation to support that patch that will address this whole area.  I'll put the whole thing onto the wiki as soon as my 9.0 related work settles down.

-- 
Greg Smith  2ndQuadrant US  Baltimore, MD
PostgreSQL Training, Services and Support
greg@xxxxxxxxxxxxxxx   www.2ndQuadrant.us