why does ansys mechanical use the SSD instead of the RAM?

- July 21, 2021 at 8:17 pm
  
  hytech
  Subscriber
  
  Hi, i am having a problem when trying to solve a nonlinear elastoplastic model of about 1500000 nodes. the solver output says that the total memory required is 108 GB and my RAM is of 128. however, the solver uses the SSD while the RAM is at 40% or less of it´s capacity. of course this implies a much larger solve time or in some cases errors (when there is not enough memory in the SSD).
  
  thanks in advance
- July 22, 2021 at 12:27 am
  
  peteroznewman
  Subscriber
  
  The solver estimates how much RAM is required to run in-core.
  Did the solver say it started in-core or out-of-core? If is says it started out-of-core, you can force it to start in-core by using a command object with this code:
  DSPOPTION,,incore
  Note that there are two commas. This assumes you are using Distributed ANSYS and checked that box.
  Even though you have more physical RAM than the estimate, it may switch from in-core to out-of-core during the solution because more RAM was required during the computation than was estimated at the beginning.
  You can have the best chance of success if you Restart the computer and only run the solver and no other software to maximize the size of a free block of RAM.
  If you really want it to run in-core, reduce the node count.
- July 23, 2021 at 12:24 am
  
  hytech
  Subscriber
  
  thanks for your reply.
  tha command you recommend, where in the model tree should i put it?
  if eventually the RAM requiered exceeds the available, does this command results in an error or will it run anyway using the SSD?
  thanks again
- July 23, 2021 at 3:00 am
  
  peteroznewman
  Subscriber
  
  I think you put that command in the Static Structural branch, but maybe it goes in the Solution branch. I'm not sure. Try putting it in both places. It will be ignored in the branch it doesn't belong.
  If the solver runs out of RAM, it will automatically switch to out-of-core.
- July 23, 2021 at 12:14 pm
  
  hytech
  Subscriber
  
  thanks for your help. i┬┤ll try that. but i want to show you the output of my last simulation:
  is this nomal? look at the amount of of memory used of the disk, while there is a lot of RAM left.
- July 23, 2021 at 9:35 pm
  
  peteroznewman
  Subscriber
  
  Yes, that is all normal.
  It looks like the model solved in RAM. It had to read the model off the disk and write the results to the disk.
- October 13, 2022 at 7:56 am
  
  thomas james
  Subscriber
  
  An SSD is non-volatile and permanently saves data, whereas RAM is a compressed sort of memory. This implies that the SSD saves data even while it is off, whereas the RAM needs to be refreshed continuously. A 256GB SSD and 8GB of RAM are insufficient for a computer. You must design a productive system that can complete the duties you want of it. RAM: Most folks need more than 8GB. For instance, if you like to play video games, you should have at least 16GB of RAM. It is advised that you have 32GB of RAM or more if you are a graphic artist.