[DOCS-13021] [OM] Memory requirements unclearly omit the backing mongods Created: 06/Sep/19  Updated: 29/Oct/23  Resolved: 03/Oct/19

Status: Closed
Project: Documentation
Component/s: Ops Manager
Affects Version/s: None
Fix Version/s: None

Type: Improvement Priority: Minor - P4
Reporter: Scott Kurowski Assignee: Anthony Sansone (Inactive)
Resolution: Fixed Votes: 0
Labels: None
Σ Remaining Estimate: Not Specified Remaining Estimate: Not Specified
Σ Time Spent: Not Specified Time Spent: Not Specified
Σ Original Estimate: Not Specified Original Estimate: Not Specified

Sub-Tasks:
Key
Summary
Type
Status
Assignee
DOCS-13080 Backport DOCS-13021 to v4.2 Backport Sub-Task Closed Anthony Sansone  
DOCS-13081 Backport DOCS-13021 to v4.0 Backport Sub-Task Closed Anthony Sansone  
Participants:
Days since reply: 4 years, 18 weeks, 6 days ago
Story Points: 2

 Description   

Description

A customer cited the OM hardware requirements page which states 15 GB RAM for the OM application plus 15 GB for a co-hosted backup daemon, however the actual memory use for their OM application was ~40 GB plus ~13 GB for the backing mongod servers, plus ~17 GB for the backup daemon mongod:

  PID USER    PR NI VIRT  RES SHR S %CPU%MEM  TIME+   COMMAND
 1094 mongodb 20 0 9371m 6.4g 17m S 3.9 2.5 385:45.94 mongod
 7276 mongodb 20 0 3604m 1.6g 10m S 3.9 0.6 224:20.54 mongod
 2797 mongodb 20 0 40.2g 3.2g 11m S 1.9 1.3 304:48.43 mms-app
 3458 mongodb 20 0 11.4g 8.5g 14m S 1.9 3.4 164:58.07 mongod
18974 mongodb 20 0 16.9g 15g  15m S 1.9 6.1 102:23.26 mongod

Customer requests this documentation be updated to more accurately estimate Ops Manager application server memory use expectations.

Scope of changes

Impact to Other Docs

MVP (Work and Date)

Resources (Scope or Design Docs, Invision, etc.)



 Comments   
Comment by Githook User [ 03/Oct/19 ]

Author:

{'username': 'atsansone', 'email': 'tony.sansone@mongodb.com', 'name': 'Tony Sansone'}

Message: (DOCSP-13080): Backport DOCS-13021 to v4.2
Branch: v4.2
https://github.com/10gen/mms-docs/commit/f220c504e7c77637aefd02a4d8ce818fa7036638

Comment by Githook User [ 03/Oct/19 ]

Author:

{'username': 'atsansone', 'email': 'tony.sansone@mongodb.com', 'name': 'Tony Sansone'}

Message: (DOCSP-13081): Backport DOCS-13021 to v4.0
Branch: v4.0
https://github.com/10gen/mms-docs/commit/b499062fcd4c482add7f230e01b715aa4bbbb174

Comment by Githook User [ 03/Oct/19 ]

Author:

{'username': 'atsansone', 'email': 'tony.sansone@mongodb.com', 'name': 'Tony Sansone'}

Message: (DOCS-13021): Added note about memory to OM requirements.
Branch: master
https://github.com/10gen/mms-docs/commit/555249386d6ad55a027546eef7f7c86312cadf47

Comment by Scott Kurowski [ 30/Sep/19 ]

I think prepending "resident" on OM memory use references would do more to make this issue go away for customers.

Comment by Anthony Sansone (Inactive) [ 12/Sep/19 ]

scott.kurowski: The output of the top command may have been misinterpreted. Reviewing this output:

  PID USER    PR NI VIRT  RES SHR S %CPU%MEM  TIME+   COMMAND
 1094 mongodb 20 0 9371m 6.4g 17m S 3.9 2.5 385:45.94 mongod
 7276 mongodb 20 0 3604m 1.6g 10m S 3.9 0.6 224:20.54 mongod
 2797 mongodb 20 0 40.2g 3.2g 11m S 1.9 1.3 304:48.43 mms-app
 3458 mongodb 20 0 11.4g 8.5g 14m S 1.9 3.4 164:58.07 mongod
18974 mongodb 20 0 16.9g 15g  15m S 1.9 6.1 102:23.26 mongod

We want to examine the RES value: physical memory. (See the top man page.)

Across all five processes, this adds up to 34.7 GB of physical memory, which is well within the stated hardware requirements (assuming < 2,000 hosts and 2 TB of blockstore storage):

  • 15 GB for Ops Manager
  • 15 GB for Backup Daemon
  • 8 GB for application database
  • 16 GB for backup database
  • 62 GB in total

The top command shows that these five processes are consuming a total of 13.9% of available physical memory. The host in question has more than 250 GB of physical memory available.

The other value, VIRT, includes "the total amount of virtual memory used by the task. It includes all code, data and shared libraries plus pages that have been swapped out and pages that have been mapped but not used." (Emphasis mine.) This is the total amount of virtual memory that has been used recently and may be used in the near future.

I don't believe the requirements need updating as these values appear within the recommended values.

Barring any further clarification, I will close this ticket at the end of business on Thursday.

I hope this helps!

mihai.bojin, please correct me if I have misunderstood this information or the requirements as documented need additional clarification.

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