On 4/4/2014 12:08 PM, Scott Marlowe wrote:
> You don't technically need the BBU / flashback memory IF the
> controller is in write through.
if you HAVE the BBU/flash why would you put the controller in write
through?? the whole POINT of bbu/flashback is that you can safely
enable writeback caching.
my testing with postgresql OLTP benchmarks on Linux, I've found
virtually identical performance using mdraid vs hardware raid in the
same caching mode. its the writeback cache that gives raid cards like
the LSI Megaraid SAS2 series, or HP P420, or whatever, their big
advantage vs a straight JBOD configuration.
--
john r pierce 37N 122W
somewhere on the middle of the left coast