How much RAM for this VM?



  • We have a windows server with the memory below.
    Server is running web applications with an database backend.
    memory.png

    Should I interpret this as there is 10.9 GB in current use and then an additional 14.6 GB in cached files?
    And "committed" is the page file, 28.1 GB in use out of it's 37.2 GB size?

    The VM has 32 GB allocated RAM. How low could we reasonably go without running into a performance penalty?



  • Additionally, this VM is running on the customers VMware server. Does VMware have dynamic allocation of RAM for it's guests so you can overcommit RAM allocation? If it does, maybe allocated RAM doesn't matter much - like thin provisioning when it comes to storage.



  • @Pete-S said in How much RAM do we need?:

    How low could we reasonably go without running into a performance penalty?

    Often the case is that there is a penalty but no one has noticed. "Slower than it could be" is not the same as "too slow." The amount of RAM you need is the amount for the company to be happy. Generally you can go a bit faster than that, but people either might not notice, or they do notice but it isn't enough to ultimately matter.



  • @scottalanmiller said in How much RAM do we need?:

    @Pete-S said in How much RAM do we need?:

    How low could we reasonably go without running into a performance penalty?

    Often the case is that there is a penalty but no one has noticed. "Slower than it could be" is not the same as "too slow." The amount of RAM you need is the amount for the company to be happy. Generally you can go a bit faster than that, but people either might not notice, or they do notice but it isn't enough to ultimately matter.

    You're right, it makes total sense to look at it from the users perspective and not from a technical perspective.

    As long as the server has enough RAM to work, then how much you allocated depends on how fast you want it to be.



  • Do they have a vCenter running that controls that host? You can run some useful charts there that tells you how it was utilised over a certain time. I have one of VMs set up as per its vendor's requirements with 24 GB of RAM and I can't touch it otherwise they won't support it. This is how much this production VM has used its allocated memory over a year:)
    b6c604da-2031-49dc-b4c9-a9ec62a4a3a7-image.png



  • @taurex said in How much RAM for this VM?:

    Do they have a vCenter running that controls that host? You can run some useful charts there that tells you how it was utilised over a certain time. I have one of VMs set up as per its vendor's requirements with 24 GB of RAM and I can't touch it otherwise they won't support it. This is how much this production VM has used its allocated memory over a year:)
    b6c604da-2031-49dc-b4c9-a9ec62a4a3a7-image.png

    why does the consumed have those dips?



  • @Dashrender because there are rises and falls in RAM requirements based on whatever this VM is doing. . . .



  • @DustinB3403 said in How much RAM for this VM?:

    @Dashrender because there are rises and falls in RAM requirements based on whatever this VM is doing. . . .

    I can understand the red line - usage doing that... but the blue line - consumption - I wouldn't expect to see dipping at all. If you've assigned 24 RAM to it, that should just be constant, unless the system has Dynamic RAM allocation enabled....

    even more, assuming this is to scale, the first dip looks to be about a month long, then raised, but not to 24, then a second raise to 24.



  • @Pete-S said in How much RAM for this VM?:

    @scottalanmiller said in How much RAM do we need?:

    @Pete-S said in How much RAM do we need?:

    How low could we reasonably go without running into a performance penalty?

    Often the case is that there is a penalty but no one has noticed. "Slower than it could be" is not the same as "too slow." The amount of RAM you need is the amount for the company to be happy. Generally you can go a bit faster than that, but people either might not notice, or they do notice but it isn't enough to ultimately matter.

    You're right, it makes total sense to look at it from the users perspective and not from a technical perspective.

    As long as the server has enough RAM to work, then how much you allocated depends on how fast you want it to be.

    Exactly. Unless having too little leads to like beating the crap out of an SSD that you want to protect. Then some extra RAM might be a good investment for long term cost savings or something like that.



  • @Dashrender said in How much RAM for this VM?:

    why does the consumed have those dips?

    I'd say this was invoked by the apps running on it. This VM is used for analytics and reporting, it's got Visual Studio, Power Bi and SQL server running on it. The vendor must've been doing some shit on it.