Which three metrics are checked to diagnose a memory bottleneck at the ESXi host level?

A company runs several instances of an application that requires large amounts of memory.
Which three metrics are checked to diagnose a memory bottleneck at the ESXi host level? (Choose three)

A.
MEMSZ

B.
MEMCTL

C.
SWAP

D.
ZIP

E.
MCTLTGT

Explanation:
THIS IS A HIGHLY DEBATED QUESTION – SOOoooo If you think it is wrong please research thoroughly before requesting an update… an official response from VMware would be nice. 😀

3 metrics to diagnose a memory bottleneck at the ESXi host level: MEMSZ, MEMCTL, SWAP.

MEMSZ – Amount of physical memory allocated to a resource pool or virtual machine.
MEMCTL – Displays the memory balloon statistics. All numbers are in megabytes.
MCILTGT – Amount of physical memory the ESXi system attempts to reclaim from the resource pool or virtual machine by way of ballooning.
SWAP – When the VMkernel on the host is swapping memory to disk

Revised; Answer is MEMSZ,MEMCTL,SWAP. Checked with VMWARE on this. Renegade_ZA

Ref: http://cosonok.blogspot.com/2011/11/using-memsz-memctl-swap-to-diagnose.html

6 Comments on “Which three metrics are checked to diagnose a memory bottleneck at the ESXi host level?

  1. Ed B says:

    I picked B, C, and D

    MEMSZ – Amount of physical memory allocated to a resource pool or virtual machine.
    MEMCTL – Displays the memory balloon statistics. All numbers are in megabytes.
    MCILTGT – Amount of physical memory the ESXi system attempts to reclaim from the resource pool or virtual machine by way of ballooning.
    SWAP – When the VMkernel on the host is swapping memory to disk
    B – Memory balloon is higher, when vmware needs to take away memory already allocated to VM
    C – Memory swap to disk is classical memory shortage
    D – ZIP indicates memory is compressed, which also show memory shortage

  2. mr_tienvu says:

    I found the following post relating with this question.
    http://cosonok.blogspot.com/2011/11/using-memsz-memctl-swap-to-diagnose.html
    ………………
    Using MEMSZ, MEMCTL, SWAP to diagnose a memory bottleneck in ESXi
    Following on from a comment posted on a previous posts, here’s a quick explanation of why MEMSZ, MEMCTL, and SWAP can be used to diagnose a memory bottleneck at the ESXi host level.

    First: Definitions

    From: http://pubs.vmware.com/vsphere-50/index.jsp

    MEMSZ (MB) = amount of memory allocated to a virtual machine.
    SWAP (MB) = displays the ESXi swap usage statistics.
    MEMCTL (MB) = displays the memory balloon statistics.

    Second: Why we might want to look at these?

    SWAP – if an ESXi host is excessively swapping memory to disk, this points to the ESXi host suffering memory contention issues, VMs should either be moved or powered off from the host in question (if this is not an option then it is time for either a memory upgrade or to introduce a new ESXi Host into the environment.)

    MEMCTL (MB) & MEMSZ (MB) – need to look at these two metrics together. Ballooning as displayed by MEMCTL is not always a problem and could indicate that guest VMs have been over allocated memory (see MEMSZ for guest memory allocation.) If have been careful to correctly allocate memory to guest VMs then excessive ballooning again points to the ESXi host suffering memory contention issues; basically the host is taking memory away from inside guest VMs by using the memory balloon driver installed along with VMware tools, this memory is written to the vswp file.

    Remember that – unlike in the physical world – in the virtual world throwing too much resource at a virtual server can actually result in less performance.

    Third: Where can we see these?

    Easiest way is to SSH to the ESXi host (the host in the example below is a vSphere 5 host,) run the command

    esxtop

    Type a lowercase m when in esxtop to display memory stats as shown in the image below (SWAP, MEMCTL, and MEMSZ are circled in red):

    [Image]

  3. JK says:

    Definitely B,C,D. You look at the memory shortage at the host level, MEMSZ just indicates memory allocated to VM, nothing to do with shortage of memory. ZIP however indicates memory compression which is one of memory reclamation techniques and kicks in when there is shortage of memory on the host.


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