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Virtual Memory 100% Utilization

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by snapp1337

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Is it uncommon for NT/Citrix to have it's virtual memory to reach 100% utilization? We have alot of RAM and have setup our vm settings according to Microsoft's specs, often we have to go even bigger. However, we still show that VM gets alot of usage. This does not lock up our servers but we were wondering. Does anyone else notice this and is this normal. Thank You lsnapp@uhhg.org

9 replies

by ann777

Virtual memory is a combination of physical memory, file system cache, and contiguous disk space. The system stores programs and data on disk until it is needed, then it moves it into physical memory. code and data no longer in active use is written back to the disk. But, when a computer does not have enough memory, program code and data must be written and retrieved from the disk more frequently... this can become a system bottleneck.

I recommend that you run performance monitor and lookat the following counters:
Pages/second
Available bytes
Committed bytes
Pool nonpaged bytes

-pages/second should be low... acceptable range is between 0-20

-available bytes should be high... acceptable is anything above 4 megebytes

-committed bytes should be low... acceptable is anything less than the amount of physical RAM you have on that server

-pool non-paged bytes should be steady... acceptable if there is no increasing.

If any of the first three is above acceptable -- you should add RAM to that system.

If the last item... increases, then you need to find out which of the running applications is creating the memory leak.

by snapp1337

We know what the definition of VM is, we are just getting conflicting information as to weather or not it is ok to see VM peak at 100%. Some say it is ok, some say it should never be over 90%. Any insite to a % level of what we should be at? Thank You

by mike (from canada)

I look at it this way. The more virtual memory you allow windows to use, the slower your applications run. The less virtual memory you allow, the faster applications run, although you might get "Out of memory" errors. so I recommend having the virtual memory set to auto because you are most likely to run many applications all requiring different amounts of memory. So to be honest, I stay with auto. in the memory management section of windows, you will see "Let Windows manage my memory (Recommended)" or something like that. Make sure that is selected.

by snapp1337

Unfortunly in Citrix you have to manually specify the virtual memory settings. 95/98 you can have windows adjust automatically, but this is not an option in NT.

by bobby gillette

An occasional peak of 100% isn't all that uncommon with any memory configuration, regardless of how large you set your pagefile. The key is how long that 100% utilization hangs around.

We also run Citrix in our environment, using either NCs or the ICA client (7 server farm to be exact with load-balancing). You have to keep in mind that when users access the Citrix server even for the logon process, the processor might peak for a split second... for that matter should they open a published app or start a process the server may also peak at 100%. What you have to do is monitor your memory usage at various times during the day, then chart your findings. If you are averaging 30-50% usage on your pagefile (that or <100 pages/sec in PerfMon),you're fine.

Without knowing more about your environment, I'd say you've set your pagefile a tad high (MS recommmends your pagefile be set to the amount of system RAM + 11MB), try setting it to no more than double your RAM. If you still experience problems, I would definitely suggest adding additional physical RAM to your server rather than increasing the size of your pagefile (as NT reserves a portion of physical RAM for each process).

Remember the addage: He who dies with the most RAM wins ;)

Hope this helps....

by snapp1337

This is what I thought. I was trying to explain this to a couple of my co-workers who were questioning this. We use a product "Concord" to give us trending, but it kept stating that our VM was at 100% all the time. I knew this wasn't the case and proved to the company that their software was pulling bad information. We have approx 1.7 GB of RAM per server, and we are now thinking about setting our VM to as low as possible and force the apps to use physical RAM. Thank you for your help in clearing up our confusion.

by bobby gillette

An occasional peak of 100% isn't all that uncommon with any memory configuration, regardless of how large you set your pagefile. The key is how long that 100% utilization hangs around.

We also run Citrix in our environment, using either NCs or the ICA client (7 server farm to be exact with load-balancing). You have to keep in mind that when users access the Citrix server even for the logon process, the processor might peak for a split second... for that matter should they open a published app or start a process the server may also peak at 100%. What you have to do is monitor your memory usage at various times during the day, then chart your findings. If you are averaging 30-50% usage on your pagefile (that or <100 pages/sec in PerfMon), you're fine.

Without knowing more about your environment, I'd say you've set your pagefile a tad high (MS recommmends your pagefile be set to the amount of system RAM + 11MB), try setting it to no more than double your RAM. If you still experience problems, I would definitely suggest adding additional physical RAM to your server rather than increasing the size of your pagefile (as NT reserves a portion of physical RAM for each process).

Remember the addage: He who dies with the most RAM wins ;)

Hope this helps....

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