Hey Dave,
Thanks for the information, for platform we will be using Debian flavors of linux as the host for the IOCs and so far have not encountered running multiple IOCs of the epics 3/7. I was concerned with spawning out so many IOC instances
if I did go with the design of one ioc one device (looking at say 30+ IOCs on one host vs combining down to ~5). I can see the benefit of efficiency when records need to communicate between each other but in this case the digitizers/dmms do not have any dependencies
on each other.
Couple other thoughts
I was looking at starting to use procServ but was a little confused from reading about the documentation on its use. What is the difference between spawning multiple IOCs through running your st.cmd for each and instead spawning them using
procServ? Is the IOC treated differently in linux when using procServ to start them?
Will I run into resource issues (on a highend desktop) spawning so many IOCs (~30) on one host (I did implement Ralphs script already to solve the multiple ioc ca issue)?
Are there concerns when running say 8 devices using streamdevice in a single IOC, I would assume there might be some delay when streamdevice has to make multiple calls in the same IOC?
From: D Willimoto <dwilliams at kiesbar.com>
Sent: Tuesday, March 30, 2021 1:52 PM
To: Manoussakis, Adamandios <manoussakis1 at llnl.gov>
Subject: Re: Question on Multiple Instruments in one IOC or Multiple IOCs for each
The platform is one dependency. Some platforms have trouble instantiating multiple IOCs of certain EPICS versions. It's difficult to do on a RaspPi for instance.
I use RaspiPi to connect to a vacuum and power supply system and I combine them into one IOC for this reason.
From a design perspective, there are two contrary forces. First, encapsulation of device as an object and address.
Second is the power of records to be actions and perform modifications. For instance a record can be a calculation from two other records. If so, you want those two source records in the same IOC to eliminate constant communication lag.
This factor also exists with other database systems like Elastic, Splunk, etc.
There are other perspectives but these are the main practical ones in my view.
Hello,
From a design perspective, is it better to have one device per IOC or would it be more efficient to group same devices into one IOC? I have multiple same instruments (digitizers,
DMMs) and was thinking to create one IOC with say 8 Digitizers or 8 DMMs but wasn’t sure if this was the way to go about this. If its better to go the other direction 1 device 1 IOC, is there a better way to spawn out the IOCs (I would guess a bash script
with variables for any of the values that need to be changed eg. IP address for each)?
Thanks,
Adam