RE: RAC - mix Intel and AMD in same cluster ?
- From: "Crisler, Jon" <Jon.Crisler@xxxxxxx>
- To: "Bobak, Mark" <Mark.Bobak@xxxxxxxxxxxx>, "oracle-l" <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 23 Jul 2009 17:52:21 -0400
Interestingly enough, the hardware we have is identical to yours. One of
the things I am considering is upgrading the AMD Opterons from dual core
to quad-core, but the dual core run at 3 ghz while he quad-core is only
2.4 ghz. So I have to look at other things like L1 and L2 cache, cache
speed etc. and see how they compare in various benchmarks.
-----Original Message-----
From: Bobak, Mark [mailto:Mark.Bobak@xxxxxxxxxxxx]
Sent: Thursday, July 23, 2009 5:42 PM
To: Crisler, Jon; oracle-l
Subject: RE: RAC - mix Intel and AMD in same cluster ?
Hi Jon,
I had a similar concern recently, as we have a 3-node cluster of DL-585
G2s, and we were looking at adding two DL-585 G5s. The advice I got was
that it may not be the best idea. Certainly, it will work, that's not
the issue. And the question isn't really AMD vs. Intel, it's more about
the CPU capacity of the newer nodes vs. the older nodes, and how many
cores you're running, in terms of the number of CPU licenses. The issue
is that, due to the way that RAC works, the performance of the newer
nodes will be gated at the performance of the older, slower node. So,
in our case, we've got 3 G2s w/ 4 dual core CPUs, and we were looking at
adding 2 G5s with 4 quad-core CPUs. Due to the extra licensing cost of
the two newer nodes, and the limited performance of the nodes when in a
cluster w/ slower performing nodes, it's actually cheaper to get 3 new
G5s and re-purpose the G2s for something else.
The reasoning behind why faster nodes in a cluster are gated to the
performance of the slowest node, is that all nodes potentially
participate in any SQL execution, even if it's not parallel. That's
because lock mastering of data blocks is hashed to all the nodes. So,
as soon as one of the slower nodes starts having CPU problems, lock
management will suffer across the cluster, and everybody slows down.
So, even though you may have a couple of nodes capable of much more CPU
load, their performance suffers due to the fact that they must
participate in the cluster, and the cluster is limited by the slowest
node.
Hope that helps,
-Mark
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Crisler, Jon
Sent: Thursday, July 23, 2009 4:54 PM
To: oracle-l
Subject: RAC - mix Intel and AMD in same cluster ?
Has anybody here built or upgraded a 10g RAC cluster using a mix of both
Intel and AMD processors ? We have an existing 3 node RAC cluster, RH
Linux 4 with AMD Opteron 3 ghz dual core cpu's. It is being considered
to add a 4th node but with Intel CPU since the servers we used ( HP DL
585 G2 ) are no longer available new. Any thoughts in mixing Intel and
AMD processors in the same cluster ? We are also looking at upgrading
the existing processors from dual-core to quad-core, but the quads seem
to max out at 2.4 ghz while the duals go to at least 3.2 ghz. Obviously
OS and Oracle will stay same version, but we might be forced to use
Intel to add additional nodes, assuming it even works.
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