5.5.1 MPIT Storage Snapshots
A tenant can create up to 24 multiple point-in-time storage snapshots. Currently, the service provider cannot limit this number. In theory, a storage snapshot can grow to the full size of the base disk if all disk block data has changed. This is very rare, however, and as a general practice, two to three times the size of each virtual machine disk should be reserved.
Upon failover (migration), the MPIT storage snapshots are not automatically consolidated because the process is time consuming and could impact virtual machine Recovery Time Objective (RTO). Service providers must therefore regularly consolidate these VMs because MPIT files take unaccounted for storage space and its delta disks negatively impact virtual machine storage performance. Consolidation can be scheduled automatically against the resource vCenter Server with the following VMware PowerCLI™ script:
Get-VM |
Where-Object {$_.Extensiondata.Runtime.ConsolidationNeeded} |
ForEach-Object {
$_.ExtensionData.ConsolidateVMDisks()
}
Note This consolidation does not impact VMs/disks that are in replication state.
Both the provider and tenant can track disk usage of each replication and MPIT with vCloud API:
• List all replications at Org VDC level
GET /api/org/<org-id>/replications
• List space requirements for replicated VM (per disk)
GET /api/admin/vr/replications/<replication-id>/details
• List total space requirements and each transfer session size and duration
GET /api/vr/replications/<replication-id>/instances
<ns2:ReplicaSpaceRequirements>6486491136</ns2:ReplicaSpaceRequirements>
<ns2:Instance>
<ns2:Id>GINST-Hbr.Replica.GroupInstance.000000000000014c/CGID-5345cefe-3ad9-457a-8452-93759e8e54d6</ns2:Id>
<ns2:TransferStartTime>2016-10-12T12:36:48.000Z</ns2:TransferStartTime>
<ns2:TransferSeconds>46</ns2:TransferSeconds>
<ns2:TransferBytes>1151172608</ns2:TransferBytes>
</ns2:Instance>
<ns2:Instance>
<ns2:Id>GINST-Hbr.Replica.GroupInstance.000000000000013a/CGID-5345cefe-3ad9-457a-8452-93759e8e54d6</ns2:Id>
<ns2:TransferStartTime>2016-10-12T10:22:22.000Z</ns2:TransferStartTime>
<ns2:TransferSeconds>1</ns2:TransferSeconds>
<ns2:TransferBytes>598016</ns2:TransferBytes>
</ns2:Instance>
Figure 22. Tenant View of Storage Consumption in vSphere Web Client
