It’s depends mainly on kind of Unix you will use (HP, Solaris, AIX, Linux, …) and the type of data and processes to manage, types of adapters also.
What will be the advantage of having different IS running on the same environment ?
If really you need differents IS, I suggest to think about virtualisation, that will help platform management and scalability, especially if one day to have to spread the workload on different hardware.
In fact we have already our project installed in a windows environment, with webMethods 6.1.
The configuration of the windows environment is as following :
Three virtual machines using Windows 2003, each having 2GB of RAM, 40 GB of disk and using a CPU of 2.33 Ghz
As you mentionned in your post we use virtual machines in Windows. But we are not sure whether virtual machines could be installed in an Unix environment (FYI we will use HP Unix).
We wish to transfer the project into an Unix environement and at the same time upgrade the webMethods software.
Erratum : There will be on average 4 Integration Servers per virtual machine. One of them will contain all the external brokers. This environment is a copy of the client infrastructure, hence we can not modify it.
We are running also under HP-UX on Itanium boxes and virtual machines works very well.
Anyway, 2 GB seems to me very short as it’s at least the memory we reserved for the JVM itself (our current 6.1 B2B server is quite loaded).
Take in account also if you’re using SAP adapter that we had to switch to 64b version of the JVM implying a memory increase (to early to determine the amount but for some tests, it’s 40 to 50% !).
Another point, even if the situation is improving, HP-UX is not the most known platform at wM. W/ 6.1 we suffered for several problem related to the HP-UX JVM and wM takes long time to qualify and solve those issues.
In our case, we reserved 2 GB per IS (heavily used) and 0.5 GB per broker server (not heavily used up to now). But we are on very early stage in our migration process so we reserved more resources is needed.
Unfortunately, we don’t have any idea about MWS and MetadataLibrary consuption so we keep default value, again with some security reserves.
In our case, the environment will be used for development.
We would not need all the IS at the same time, and we will not use it heavily.
What I would have liked to know, is wether you changed the RAM level when moving from Windows to Unix. Or in other words, does webMethods consume more RAM, CPU in Unix than Windows.