Re: Poor RAC inter-instance performance

"Ivan Vasquez" <ivan_at_looker.itos.uga.edu> wrote in message news:<c4aafk$897$1_at_cronkite.cc.uga.edu>...
> 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.

Ivan,

Do you have both a public and private interconnect? It is not clear from your post if this is the case.

Mike Ault Received on Tue Mar 30 2004 - 14:04:58 CST