VSAN Part 13 – Examining the .vswp object

I’ve seen a few question recently around the .vswp file on virtual machines. The .vswp or VM swap is one of the objects that go to make up the set of virtual machine objects on the VSAN datastore, along with the VM Home namespace, VMDKs and snapshot delta. The reason for the question is that people do not see the .vswp file represented in the list of virtual machine objects in the UI. The follow-on question inevitably is then around how do you see the policy and resource consumption of a virtual machine’s .vswp object.

This is in fact quite tricky, because even if you try to use the RVC command, vsan.vm_object_info, you only get information about VM Home Namespace, VMDKs and deltas. Again, there is no information displayed for the VM swap. To get information about the .vswp, you first of all have to retrieve the UUID information from the virtual machines .vswp descriptor file.

# cat win1-6e39614a.vswp
# Object DescriptorFile
version = "1"

objectID = "vsan://c7c0a552-7851-b20b-8d05-1cc1de253a92"
.
.

Once you have the descriptor, this can then be used in RVC to display information about the actual swap object. The command to do this is vsan.object_info. This RVC command takes two arguments; the first argument is the cluster and the second argument is the UUID.

/localhost/CH-Datacenter/computers> ls
0 CH-Cluster (cluster): cpu 86 GHz, memory 45 GB
/localhost/CH-Datacenter/computers> vsan.object_info 0 c7c0a552-7851-b20b-8d05-1cc1de253a92
DOM Object: c7c0a552-7851-b20b-8d05-1cc1de253a92 (owner: 10.20.177.17, policy: hostFailuresToTolerate = 1, forceProvisioning = 1, proportionalCapacity = 100)
  Witness: 048fa852-ac82-539b-a3ed-1cc1de253a92 (state: ACTIVE (5), host: 10.20.177.19, md: naa.5000c5002bd78a5f, ssd: naa.50015178f35d87ac)
  RAID_1
    Component: fc8ea852-0603-7190-4bf6-1cc1de253a92 (state: ACTIVE (5), host: 10.20.177.18, md: naa.5000c5002bd62be3, ssd: naa.50015178f35d86ee)
    Component: 4d6aa852-0238-f7e6-c93c-1cc1de253a92 (state: ACTIVE (5), host: 10.20.177.17, md: naa.5000cca00b33fc20, ssd: naa.50015178f35d8e33)

/localhost/CH-Datacenter/computers>

(Drag the above from right to left to see the full output) Now that we have the .vswp object info, we can see a number of things:

• FailuresToTolerate for .vswp is set to 1. This gives us a RAID-1 (mirror) configuration for VM Swap.
• ProportionalCapacity for .vswp is set to 100%. This means that the space needed for swap is indeed fully reserved.

What can be deduced from this is that from a space utilization standpoint, the VM swap of a virtual machine deployed on VSAN will consume (Configured Memory – Memory Reserveration) * (Failures to Tolerate +1) amount of space on disk.

Of course, the plan is to eventually get this plumbed up into the UI in RVC to make it more easily accessible, but for now this method will hopefully allow you to gather this information should you need it. The VM swap (.vswp) is an important consideration when sizing your VSAN storage.

For more information on VSAN objects and components, please refer to this post here. All VSAN blog posts can be found here.

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