Exchange 2010 -- needs more memory ?

My friend has the below
  ** Exchange 2010
  ** Windows 2008 R2, will upgrade soon

https://technet.microsoft.com/en-us/library/ee832793.aspx shows the minimum required physical memory should be 20GB for 100 mailboxes, but he has 150 mailboxes, with memory almost 100% used which is normal for Exchange

1. Do you think he should really have 30+ GB of memory for 150 mailboxes ?
2. How can I find when Exchange needs MORE memory since I was told Exchange 2010 always runs at 100%, even after adding more memory ?
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timgreen7077Exchange EngineerCommented:
the article is database count and not mailbox count. if the server is performing fine there is no need to increase the memory. 150 mailboxes should be fine with 20GB of memory. the only reason I can think to. increase memory is if the server is running multiple roles other than just the mailbox role.
Wayne88Commented:
I would increase the RAM If you are having performance issues.  For example, symptoms like slowness or laggy response when you are directly working on the Exchange server may point to a RAM problem.

If you are satisfied with the server's performance and no users are complaining then I don't think you need to add more memory.  Having said that, if you can spend the $ for more RAM then it will definitely be better.  Shouldn't be that expensive.
timgreen7077Exchange EngineerCommented:
you can run the following cmd to get a list of roles for the server

Get-ExchangeServer | select name, serverrole, edition | fl
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Seth SimmonsSr. Systems AdministratorCommented:
Do you think he should really have 30+ GB of memory for 150 mailboxes ?

should be fine
my server has ~110 mailboxes with 16gb and works fine

How can I find when Exchange needs MORE memory...

as mentioned, if users are experiencing performance issues
also, if you see warnings in the application log that a significant portion of the database buffer cache was written to the page file, could be a sign you need more memory

seems like your server is fine the way it is
Mal OsborneAlpha GeekCommented:
Yep, when Exchange reads data from the store on disk, it keeps it in cache for ever, or until something else needs the memory. This makes sense; RAM is far faster than HDD, and there is no point clearing memory if it is not needed for anything else. An Exchange server can use as much memory as the entire store, if everything in every mailbox is read at some time.

With more RAM, more data will be cached,  when a  user opens an email it will more frequently be read from RAM rather than disk, performance, on average will be better, and the hard drives will be less busy.

So, moving from 20Gb of RAM to 30Gb would in theory make things faster, it would  probably be difficult to discern. Also, what level of performance is deemed acceptable varies. Other factors of course come into play, are users sending 10 emails per day, or 100 or 1000? How fast is the disk subsystem? What is the average email size? How frequently do users run searches? How many mailboxes are shared? Is access generally via a Gigabit LAN, or OWA over a slow, remote connection? Is each mailbox 10Mb or 1GB or 100Gb?

I would suggest that if users find the current level of performance acceptable, the server be left as it is. Going from 20Gb to 30Gb probably not make much difference anyway. If performance is perceived as lacklustre, then it is probably worth adding at least another 20Gb, if you have it to spare.
Robinsan ShawFreelancer BloggerCommented:
In the article that you have mentioned above, it is clear that for every 50 mailboxes count, you must have 10GB of memory.
1.png
So, as per the above tabular information it is easy to determine that:
 33.png
So, I think your friend should have at least 30 GB space for 150 Mailboxes not to hinder the performance.

And if I talk about Exchange 2010 server memory configuration, below tabular information can help you.
2.png

Moreover, memory configuration depends upon many factors like the performance of the application, utilization of the mailboxes and after analyzing these factors you can increase the memory for Exchange 2010 Server.

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