Ivan Vasquez wrote:
>>>I'm testing a 2-node Linux RAC installation that's performing poorly
>>> under
>>>certain circumstances. The cluster is using 1G NICs as interconnect. I
>>>already know I'm not supposed to ask for great performance out of it,
>>>however the interconnect's capacity is far from reached whenever I
>>> notice bad performance.
>>>
>>>Here is the behavior:
>>>
>>>With only one instance up, any query runs quickly, as expected.
>>>
>>>With both instances up, I connect to instance A, run a long query (say,
>>>30-seconds) and it runs normally. At this point I assume instance A has
>>>cached some or all the blocks used for the query.
>>>
>>>Then I connect to instance B and issue the same query as above. Rows are
>>>returned intermittently, up to 4-second delays in between. I assume in
>>
>>this
>>
>>>case RAC is trying to ship whichever buffers are found in instance A
>>
>>instead
>>
>>>of reading from disk. No DML activity is going on, it's just me and the
>>>database.
>>>
>>>What confuses me is that I don't see much traffic thru the interconnect,
>>
>>and
>>
>>>CPU and disk utilization are far from high. Using vmstat I see increased
>>>context switches, but they are just as high as those in the instance
>
> that
>
>>>runs fine! I have read note 181489.1 but haven't found much help from it
>>
>>and
>>
>>>wonder if it's something else inherent to my architechture (i386).
>>>
>>>Thanks in advance for any clues.
>>>Ivan.
>>>
>>>
>>
>>
>
>
--
Daniel Morgan
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Received on Tue Mar 30 2004 - 15:40:02 CST
