Min # of servers per pool v/s actual number of servers

Answered

Alvaro Palma

• February 05, 2021 13:59

Hi guys. I'm testing Gurobi Instant Cloud, and I set my pool using:

Min Servers = 1
Job Limit   = 1

My idea is never having more than one job running on each server, since my cases are MIP that heavily rely on MT, hence, more than one job in the same server will imply each core running more than one process per time, and that's certainly not the idea.

After that, I launched 15 jobs in my local farm, but I noticed only 1 was scheduled, no more servers than just 1 were started. Manually I could scale up the pool to 10 servers, but even then, 5 jobs remained queued.

So, my questions are:
1. Does "Min Servers" also stand for "Max Servers"?
2. If not, what configuration am I missing that prevents me to automatically (not manually) start more than 1 server?
3. Is it possible to start more than 10 servers? If so, is that configuration related to the license?
4. No directly related, but what does "If you select more than one compute servers, load balancing will be enabled" stand for? Does that imply in any way that more than 1 job will be launch on any server, regardless of the "Job Limit" setting?

Thanks a lot for your help in advance.

1

• 

  Jaromił Najman

  Gurobi Staff

  • February 11, 2021 12:31

  Hi Alvaro,

  1. Does "Min Servers" also stand for "Max Servers"?

  I assume you mean the "Compute Servers" field in the "License" tab when creating a pool. This stands for the number of server associated in the pool.

  2. If not, what configuration am I missing that prevents me to automatically (not manually) start more than 1 server?

  When you set the "Compute Servers" field in the "License" tab to, e.g., 2, then at most 2 machines in the particular pool will be automatically started when you submit jobs.

  3. Is it possible to start more than 10 servers? If so, is that configuration related to the license?

  It is currently not possible to have more than 10 servers in a pool.

  4. No directly related, but what does "If you select more than one compute servers, load balancing will be enabled" stand for? Does that imply in any way that more than 1 job will be launch on any server, regardless of the "Job Limit" setting?

  The idea of load balancing is as follows:

  When a new job (environment) is requested for a Compute Server Cluster or Cloud, the machine that is currently using the smallest fraction of its capacity (ratio of active jobs vs. the job limit) is chosen.

  Example: If a machine with a job limit of 2 is running 1 job, and a machine with a job limit of 5 is running two jobs, the next job will go to the machine with a limit of 5.

  Best regards,
  Jaromił

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