Unanswered: Help needed : Question on Logical CPUs and ASE engines
Hi Sybase experts!
As per Sybase documentation,
max online engines = 8 This tunable option specifies the maximum number
of ASE engines that can be online at any one time in an SMP environment. The value should be set equal to the number of logical CPUs or to the number of logical CPUs - 1.
In our migration scenario, we need to migrate a Sybase instance with 12 ase max online engines configured running on 8-cpu machine (virtual CPUs reported are 16 and psrinfo -p shows 8 physical CPUs).
We need to estimate the number of CPUs in target environment for running 12 ASE engines - In target environment, the CPU will be dual core.
The question is will logical CPU map to a single core of CPU? How do we go about estimating CPU requirement for 12 ASE engines running for a single instance?
How many CPUs do you have on the target machine?
What other processes need to run?
What is the throughput ratio between the logical CPUs on the old machine and a single core on the new one?
This is all information that is necessary (but probably not sufficient) to answer your question.
Personally, if I have to do this sort of thing without adequate testing I would set the "number of engines at startup" at some reasonable number (for example if you have 8 cores on the new machine I'd set it at 4), and set "max number of engines" at some higher number (again, with 8 cores I might set it at 7).
Then when the new server is brought into production I would monitor the perfmance closely, and bring additional engines online (via sp_engine) if it appears to be necessary.
Thanks a lot for update !
We need to determine the number of CPUs required in target env based on only Sybase instances and OS overhead. UltraSPARC IV+ is processor in target env (Chip Multithreading (CMT) processor with two threads per processor) - So my understanding is we should be able to use 2 logical CPUs for 2 ASE engines (8 physical CPUs for 16 ASE engines - value summed up for all sybase instances) in this case. We may not online all the engines at startup and only set the value 'max online engines'. Hence if the total number of engines for all the sybase instances to be migrated is 16 - we are thinking of 8 cpus + additional CPU for OS overhead and processes like backup server, mon server etc. Is this approach correct? Kindly suggest.