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Question about SAP + SLES10 + vSphere and the truth about memory

Hi,

we are using vSphere and SLES 10 for a SolutionManager 7.0 on MaxDB 7.6.

The system is configured with 2 GB RAM in the VM. The database is configured to use 125000 pages as cache (100000 KB).

Yes, I know the system is configured very small for this usage, but it is a demo system...

But the system is really slow. I can't figure out whats the problem.

The RAM is configured with 2 GB in the VM a "free" in linux shows me that there is 500 MB used for file system chache

total used free shared buffers cached Mem: 2076908 2002704 74204 0 28936 578212 -/+ buffers/cache: 1395556 681352 Swap: 6185016 3037744 3147272

so this shoud be ok, for me it is close to the limit...

But VMware infrastruture client shows me, that there are only 300 MB of the 2GB is used ... but the database should use 1 GB and SAP should use some RAM , too.

So who tells the truth? Where does the RAM goes to if it is not used in VMware? Could this be the performance problem?

An other problem is, that the show dev_io of the database shows me very slow access to the files ...

i.e.

I/O via Device Processes: UNIX Devspace Read avg_read Write avg_write tid name count time count time 28596 /sapdata/SYS/sapdata/DISKD01 6532 0.0294 101 0.2077

But VMWare shows that there is nearly no usage of DISK ... average is shown as 150 KBps...

So again, who tells the truth?

What else could be the problem?

Thank you.

Best regards

Christian

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2 Answers

  • Best Answer
    May 07, 2010 at 12:04 PM

    > we are using vSphere and SLES 10 for a SolutionManager 7.0 on MaxDB 7.6.

    > The system is configured with 2 GB RAM in the VM. The database is configured to use 125000 pages as cache (100000 KB).

    2 GB is way too less.

    On a 64bit installation the Java instance alone (which is installed as part of SolMan) uses 2 GB heap memory fixed, so all your memory is allocated by the Java process. Then you have the database (with parameter CACHE_SIZE) plus the ABAP part plus the operating system.

    I would not run a SolMan with less than 6 GB of memory and carefully configuring how much is used by each of the system parts (OS, database, ABAP and Java).

    Markus

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    Former Member
    May 10, 2010 at 11:07 AM

    Hi all,

    thanks for your reply.

    Sorry, my fault, I always had in mind, that 32 bit OS could not allocate more than 3 GB (I remember SAP notes about this for Windows NT) .... but if 32 bit limits are only for each process, I am going to keep this in mind.

    I am going to request more RAM .... !!

    I am going to figure out what kind of SAN we are using .. at the moment a reboot of the system sped up the access ...

    But there is still the question who tells the truth:

    VMWare (or esxtop): showing me that the system uses 300 MB RAM

    free on linux SLES10: showing me that the system uses 2GB RAM (and 3 GB SWAP)

    please keep in mind that just the database is configured to use 1 GB RAM, so VMWare should be wrong...

    But why shows VMWare such "nonsense" RAM usage?

    If there is further information I am goin to post it.

    Best regards

    Christian

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