ahv

Nutanix AHV: Where have all the memory gone?

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In an AHV host with just the CVM and two other VMs running, there’s just about 1G of free memory. There’s 28 GB for the CVM and 8 GB each for the two other VMs. That is just 44 our of 125 GB of RAM on the host.

[root@ahv ~]# head /proc/meminfo
MemTotal:       131859556 kB
MemFree:          286384 kB
MemAvailable:    1151500 kB
Buffers:          113908 kB
Cached:           632172 kB
SwapCached:            0 kB
Active:           839356 kB
Inactive:           5600 kB
Active(anon):     106800 kB
Inactive(anon):      148 kB

This is because, from AOS 5.0, almost all memory is assigned to hugepages.

[root@ahv]# grep Huge /proc/meminfo
AnonHugePages:         0 kB
HugePages_Total:   63360
HugePages_Free:    40832
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB

This host has 123 GB (HugePages_Total * Hugepagesize) assigned to huge pages!

What are huge pages? How are they different from normal page?
See here

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Identify passthrough device in AHV

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  1. Open an ssh session to the host
  2. Run “virsh list” and note the CVM name or ID
  3. Run “virsh dumpxml CVM_ID or CVM_name”
  4. Look for lines within hostdev tags
<hostdev mode='subsystem' type='pci' managed='yes'>
      <driver name='vfio'/>
      <source>
        <address domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
      </source>
      <alias name='hostdev0'/>
      <rom bar='off'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
  </hostdev>

Mapping interfaces in a guest domain to the OVS interface

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Read Correlating OVS and Guest Domain Interfaces.

I have been using a combination of virsh domiflist domain_name and ovs-vsctl to map VM interfaces to OVS interface in an AHV environment.

From Scott’s post, I learned these new commands which are new to me.

ovs-vsctl list interface vnetX
ovs-vsctl get interface vnetX external_ids

Importing a Workstation VM to AHV fails with NFS3ERR_NOENT error

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To import a Workstation VM to AHV, KVM based Nutanix Hypervisor from Nutanix, I copied it to AHV container by WinSCPing to the the Prism IP:2222. While converting the vmdk to AHV format from Image Configuration, I got an error:

NFS: Lookup of /path/filename-flat.vmdk failed with NFS3ERR_NOENT(-2)

The error code NFS3ERR_NOENT means NFS is unable to find the file.

From RFC 1813:

NFS3ERR_NOENT
       No such file or directory. The file or directory name
       specified does not exist.

The solution is to use .vmdk and not -flat.vmdk during conversion. The default disk format in VMware Workstation is monolithic sparse which is a single growable file.

From here:

VIXDISKLIB_DISK_MONOLITHIC_SPARSE – Growable virtual disk contained in a single virtual disk file. This is the default type for hosted disk, and the only setting in the Virtual Disk API Sample Code sample program.