Exchange Back Pressure

Dear All

]My mail system is working so far as it should. Mail flow works, no claims from clients.

Anyway I've received the following warning:
- Back Pressure:

The resource pressure increased from Normal to Medium.

The following resources are under pressure:
Version buckets = 123 [Medium] [Normal=80 Medium=120 High=200]
Physical memory load = 97% [limit is 94% to start dehydrating messages.]

The following components are disabled due to back pressure:
Inbound mail submission from the Internet
Mail submission from Pickup directory
Mail submission from Replay directory
Mail delivery to remote domains
Content aggregation

The following resources are in normal state:
Queue database and disk space ("C:\Program Files\Microsoft\Exchange Server\V14\TransportRoles\data\Queue\mail.que") = 75% [Normal] [Normal=95% Medium=97% High=99%]
Queue database logging disk space ("C:\Program Files\Microsoft\Exchange Server\V14\TransportRoles\data\Queue\") = 75% [Normal] [Normal=93% Medium=95% High=97%]
Private bytes = 7% [Normal] [Normal=71% Medium=73% High=75%]
Batch Point = 0 [Normal] [Normal=2000 Medium=4000 High=8000]
Submission Queue = 0 [Normal] [Normal=1000 Medium=2000 High=4000]

I've found the following interesting article:

=> The Version buckets is not a problem so far
=> I'm bit in concern about the memory.

My system has the default roles installed -> MBX,HT,CAS and has 19GB of memory.
In the past I've extend the memory by adding + 7 GB. Now the errors cames again.

The store.exe consumes around 16 GB,
the consumes around 1.8 gb
EdgeTransport.exe around 1.5 gb

The used physical memory is by around 98%

My question:
=> the stores.exe consumes a lot of memory - so it seems to be normal that you will reach the 94% of physical memory load.
(normal behavior i understand)

Is there a way to avoid this behavior or what we can do in this case?
A next step is to consider to create a new server and move the CAS and HUB role.
thanks and regards,
teggraSystem EngineerAsked:
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JeanPoLConnect With a Mentor Commented:
well i had back pressure wihtout any-warining.
Mail were not going outside. In my research i found 2 critical points.Keep disk of database around with  15-20 gb free space  and ensure that has enough memory. thats all no need to read long microsoft article :)

and yes u have mmry problem for 100% , thats the cause of BP.
teggraSystem EngineerAuthor Commented:
Hi JeanPol,

So your suggestion is to extend the memory.
Anyway, the store.exe consumes as much as possible.
When i extend the server with 10 GB of memory...e.g. to 30GB
then I'm sure the store.exe will consume 27GB or more - as much as possible.

In this case, I will have all the time BackPressure problems - no?

(I have only 350 users running on this server :)   )

I have had a similar issue. If you're combining roles then the store cache is not reactive enough to relase memory when it's needed elsewhere. Be careful, but this does the trick...


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Alan HardistyCo-OwnerCommented:
teggraSystem EngineerAuthor Commented:

Thanks for your comment.
The problem is, yes i have multiple roles installed AND I have the forefront antivirus with 5 engines & exclaimer disclaimer running.
So all these apps need also memory - and the store.exe takes what he can.

Your suggestion was great in a lab - but in a very sensitive live environment i should be very careful.

I think it would be easier and more safety to change the roles.
Leave the existing server with the mailbox role and create  new one with the cas/hub and the additional software components like disclaimer & forefront.
Anyway i think it's a good idea because my cpu is consuming around 80-95% - it's too much.

What do you think?



Thanks for your comment.
In your post, there's a good information about make the send/receive running again - i will keep in mind thanks.
Anyway I have no disk issues - running on a netapp fibredisk storage with enough performance and capacity.
My problem is only the memory and sometimes the cpu load.

Thanks and regards,
Alan HardistyCo-OwnerCommented:
You can limit the amount of memory Exchange uses by tweaking AD with ADSIEDIT:

This should get around the problems you are having, which is perfectly normal as Exchange uses as much memory as it can get it's hands on by design, but will free this up if something else wants to use it.
well yep. If the cpu is maxing out too then you must split the roles - especially if you have the hardware to do it... \Just make sure that all the intoduction of additional hardware does not affect your availability - ie are you taking measures for nlb/ exchange store availibility?
Alan HardistyCo-OwnerCommented:
Splitting the roles will probably alleviate the problem but Exchange is designed to use as much memory as it can get it's hands on, so what you are seeing is perfectly normal.

Restricting the memory Exchange can use will leave some for other Apps and then it will mean that Backpressure won't kick in because of memory.

Splitting the roles involves new hardware / software, which is costly - adjusting the memory is a zero-cost option.
teggraSystem EngineerAuthor Commented:
I will not go ahead with non-supported scenarios, so I've decide to review the environment and go ahead with dedicated servers.

thanks to all
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