bfe2987752
1. Migrate and tidy up cloud architecture examples from the current guide 2. Migrate figures 3. Add placeholder sections for new content Change-Id: I290f555f6e0cd4200deccb4d705127d99e61c343 Partial-Bug: #1548176 Implements: blueprint archguide-mitaka-reorg
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3.8 KiB
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79 lines
3.8 KiB
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Multi-hypervisor example
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A financial company requires its applications migrated
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from a traditional, virtualized environment to an API driven,
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orchestrated environment. The new environment needs
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multiple hypervisors since many of the company's applications
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have strict hypervisor requirements.
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Currently, the company's vSphere environment runs 20 VMware
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ESXi hypervisors. These hypervisors support 300 instances of
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various sizes. Approximately 50 of these instances must run
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on ESXi. The remaining 250 or so have more flexible requirements.
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The financial company decides to manage the
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overall system with a common OpenStack platform.
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.. figure:: figures/Compute_NSX.png
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:width: 100%
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Architecture planning teams decided to run a host aggregate
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containing KVM hypervisors for the general purpose instances.
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A separate host aggregate targets instances requiring ESXi.
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Images in the OpenStack Image service have particular
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hypervisor metadata attached. When a user requests a
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certain image, the instance spawns on the relevant aggregate.
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Images for ESXi use the VMDK format. You can convert
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QEMU disk images to VMDK, VMFS Flat Disks. These disk images
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can also be thin, thick, zeroed-thick, and eager-zeroed-thick.
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After exporting a VMFS thin disk from VMFS to the
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OpenStack Image service (a non-VMFS location), it becomes a
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preallocated flat disk. This impacts the transfer time from the
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OpenStack Image service to the data store since transfers require
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moving the full preallocated flat disk rather than the thin disk.
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The VMware host aggregate compute nodes communicate with
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vCenter rather than spawning directly on a hypervisor.
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The vCenter then requests scheduling for the instance to run on
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an ESXi hypervisor.
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This functionality requires that VMware Distributed Resource
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Scheduler (DRS) is enabled on a cluster and set to **Fully Automated**.
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The vSphere requires shared storage because the DRS uses vMotion
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which is a service that relies on shared storage.
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This solution to the company's migration uses shared storage
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to provide Block Storage capabilities to the KVM instances while
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also providing vSphere storage. The new environment provides this
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storage functionality using a dedicated data network. The
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compute hosts should have dedicated NICs to support the
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dedicated data network. vSphere supports OpenStack Block Storage. This
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support gives storage from a VMFS datastore to an instance. For the
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financial company, Block Storage in their new architecture supports
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both hypervisors.
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OpenStack Networking provides network connectivity in this new
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architecture, with the VMware NSX plug-in driver configured. legacy
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networking (nova-network) supports both hypervisors in this new
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architecture example, but has limitations. Specifically, vSphere
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with legacy networking does not support security groups. The new
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architecture uses VMware NSX as a part of the design. When users launch an
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instance within either of the host aggregates, VMware NSX ensures the
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instance attaches to the appropriate network overlay-based logical networks.
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The architecture planning teams also consider OpenStack Compute integration.
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When running vSphere in an OpenStack environment, nova-compute
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communications with vCenter appear as a single large hypervisor.
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This hypervisor represents the entire ESXi cluster. Multiple nova-compute
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instances can represent multiple ESXi clusters. They can connect to
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multiple vCenter servers. If the process running nova-compute
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crashes it cuts the connection to the vCenter server.
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Any ESXi clusters will stop running, and you will not be able to
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provision further instances on the vCenter, even if you enable high
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availability. You must monitor the nova-compute service connected
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to vSphere carefully for any disruptions as a result of this failure point.
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