1. vSphere Storage ®
Appliance
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2. vSphere Storage Appliance
Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Architectural Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Managing and Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
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3. vSphere Storage Appliance
Introduction
In VMware vSphere™ 5.0 (“vSphere”), VMware is releasing a new software storage appliance to the market
called the vSphere® Storage Appliance (VSA). This appliance provides an alternative shared storage solution for
small-to-medium business (SMB) customers who might not be in a position to purchase a SAN or NAS array for
their virtual infrastructure. Without shared storage configured in a vSphere environment, customers have not
been able to exploit the unique features available in vSphere 5.0, such as vSphere® High Availability (vSphere
HA), vSphere® vMotion® (vMotion), and vSphere® Distributed Resource Scheduler (vSphere DRS). The VSA is
designed to provide shared storage for everyone.
This paper presents an overview of the VSA architecture, deployment of a VSA storage cluster, and basic
monitoring and managing.
Architectural Overview
VSA can be deployed in a two-node or three-node configuration. Collectively, the two or three nodes in the VSA
implementation are known as a VSA storage cluster. Each VMware ESXi server has a VSA instance deployed to it
as a virtual machine. The VSA instance will then use the available space on the local disk(s) of the VMware ESXi
servers to present one mirrored NFS volume per VMware ESXi. The NFS volume is presented to all VMware ESXi
servers in the datacenter.
Each NFS datastore is a mirror, the source residing on one VSA (and thus, one VMware ESXi), and the target
residing on a different VSA (and thus, a different VMware ESXi). Therefore, should one VSA (or one VMware
ESXi) suffer a failure, the NFS datastore can still be presented, albeit from its mirror copy. This means that a
failure in the cluster is transparent to any virtual machines running on that datastore.
VSA VSA VSA
vSphere vSphere vSphere
VSA Manager
vSphere Client
NFS NFS NFS
Figure 1 . Three-Member VSA Cluster
The VSA can be deployed in two configurations:
• 3 x VMware ESXi 5.0 server configuration
• 2 x VMware ESXi 5.0 server configuration
The two different configurations are identical in the way in which they present storage. The only difference is in
the way that they handle VSA storage cluster membership. The following section covers the details of a three-
node and two-node VSA storage cluster.
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4. vSphere Storage Appliance
Three-Node Configuration
In the three-node standard configuration, each node runs an instance of VSA. Each node presents a file system
via NFS that is mirrored to one other file system on another VSA. To prevent any sort of split-brain scenario, the
three-node VSA configuration requires at least two nodes to be running in order to maintain a majority of nodes.
vCenter Server
VSA Manager
Manage
VSA
Datastore 2 VSA
VSA
Datastore 1 Datastore 3
Volume 1 Volume 3 Volume 3 Volume 2
(Replica) (Replica)
Volume 2 Volume 1
(Replica)
VS VS
A A
AP AP AP
P AP
P VS P P
OS OS A OS OS
AP AP AP
AP P P
P P
ES OS
OS OS ES OS
Xi Xi
-1 AP -3
P
ES OS
Xi
-2
VSA Cluster with 3 members
Figure 2. Three-Member VSA Cluster
In Figure 2, the three NFS datastores in the oval are NFS file systems. These file systems are presented as NFS
datastores to the VMware ESXi servers in the cluster.
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5. vSphere Storage Appliance
Two-Node Configuration
The two-node VSA configuration uses a special VSA cluster service, which runs on the
VMware vCenter Server. This behaves as a cluster member and is used to make sure that there is still a majority
of members in the cluster, should one VMware ESXi server VSA member fail. There is no storage associated with
the VSA cluster service.
vCenter Server
VSA Manager VSA Cluster Service
Manage
Volume 1 Volume 2 Volume 2 Volume 1
(Replica) (Replica)
VSA VSA
Datastore 1 Datastore 2
VS VS
A A
AP AP AP AP
P P P P
OS OS OS OS
AP AP
P P
ES OS ES OS
Xi Xi
-1 -3
VSA Cluster with 2 members
Figure 3 . Two-Member VSA Cluster
In Figure 3, the VSA datastores in the oval are NFS file systems presented as shared storage to the VMware ESXi
servers in the datacenter.
VSA Installation
A VSA installation is started by installing the VSA manager software on an existing VMware vCenter Server.
NOTE: In this release of VSA, an instance of VMware vCenter Server 5.0 can only manage a single VSA storage
cluster.
Once completed, a vSphere client is opened and pointed to the VMware vCenter Server, and the VSA manager
plug-in is enabled. This creates a VSA manager tab in the vSphere client. The VSA manager tab then navigates
the customer through the remaining installation steps. During the installation, a datacenter must be selected,
after which a list of VMware ESXi servers in that datacenter is presented. The installer will check the
compatibility of each of these hosts to make sure they are suitable for VSA deployment. Out of the compatible
hosts, a maximum of three hosts can be selected to participate in the VSA storage cluster. If the hosts are
unsuitable for any reason (for example, if hardware is not supported, or networking is not configured), the installer
will report it and will not enable the user to select that particular host.
The installation process scans all of the local storage attached to the VMware ESXi host, and then makes plans to
use space not currently in use by the VMware ESXi boot image for data storage. The user is warned in several
places that any existing data will be overwritten. Once this is complete, the storage is configured as a datastore
and exported to other members in the VSA storage cluster.
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6. vSphere Storage Appliance
During the installation, the VSA installer does some additional housekeeping to enable the user to take
maximum advantage of the shared storage now available. First, the installer configures a vMotion network
between the nodes in the VSA storage cluster. This enables the user to initiate the vMotion process on any
virtual machines configured to run on the hosts that make up the VSA storage cluster. The installer also
automatically builds a vSphere HA cluster covering the VMware ESXi hosts in the VSA storage cluster. This
protects any virtual machines running in these hosts. For environments with additional hosts in the vSphere
datacenter beyond the VSA storage cluster, the user can manually extend the vMotion network configuration
and vSphere HA cluster configuration to encompass these hosts.
Managing and Monitoring
The VSA manager UI enables administrators to view the status of all VSA instances and datastores in the VSA
storage cluster. The interface is integrated into VMware vCenter, giving it a familiar look and feel, and helps an
administrator to deploy, manage, and monitor VSA instances and the VSA storage cluster.
First, we can look at the monitoring capabilities. At deployment time, each VSA will host a primary datastore
and a replica.
Figure 4 presents a view of the VSA members, shown by clicking on the Appliances button in the center-left
position of the window. In this example, it is a three-member configuration. By default, the VSA members are
labeled VSA-0, VSA-1, and VSA-2. The Hosted Datastores and Hosted Replicas columns show that each VSA
member continues to host a primary datastore and a replica. The user can also see which VMware ESXi server is
hosting the VSA via the Host column.
Finally, we can see that all the VSA members are Online via the Status column.
By selecting a VSA member, additional properties are displayed in the lower half of the screen, including front-
end/Management Network and the Back-End Network/features details.
Figure 4. VSA Manager – VSAs View
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7. vSphere Storage Appliance
A Datastores view and a Maps view are also available to assist administrators with monitoring the VSA cluster.
The VSA supports the concept of the VSA maintenance mode, both for the individual VSA instances and for the
VSA storage cluster as a whole. Maintenance mode enables administrators to take individual members or the
whole VSA storage cluster offline in a controlled and structured manner.
To put the whole cluster into maintenance mode, select the Enter Maintenance Mode link in the VSA Cluster
Properties highlighted in Figure 5.
Figure 5. VSA Manager – Cluster Maintenance Mode
NFS exports from the VSA members become inaccessible when the whole cluster is put into maintenance mode.
The cluster is still up, but the NFS services and datastores are taken offline.
An individual VSA member can also be placed into maintenance mode by selecting a member from the
Appliances view, and then clicking the Enter Maintenance Mode link. This is not the same as the VMware ESXi
maintenance mode or the vSphere DRS maintenance mode. Rather, it is a maintenance mode specific to VSA
cluster members. These actions will shut down the VSA member. If the whole cluster is already in maintenance
mode, no further action is necessary.
The best practice for using the maintenance mode is to first put the whole cluster into maintenance mode, and
then to place individual members into maintenance mode.
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8. vSphere Storage Appliance
When a VSA member is placed into maintenance mode, the following states will show up in the VSA Manager >
VSAs view:
Figure 6. VSA Manager – Maintenance Mode VSA Status
In Figure 6, member VSA-0 has been placed into maintenance mode. VSA-0 was hosting the primary datastore
VSADs-1 and the replica for VSADs-0. However, since we placed this member into maintenance mode, another
VSA member had to take over the export of the primary NFS datastore. In this case, it is VSADs-2, as shown in
the Exported Datastores column.
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9. vSphere Storage Appliance
Conclusion
VSA enables users to get the full range of vSphere features, including vSphere HA, vMotion, and vSphere DRS,
without having to purchase a physical storage array to provide shared storage, making VSA a very cost-effective
solution.
VSA is very easy to deploy. Many of the configuration tasks, such as network setup and vSphere HA deployment,
are done by the installer. The benefit here is that this product can be deployed by customers who might not be
well versed in vSphere. It gives them a good first-time user experience.
VSA is very resilient. If a VMware ESXi server that is hosting one of the VSAs goes down, or one VSA member
suffers an outage, with the redundancy built into the VSA, the NFS share presented from that VSA will be
automatically and seamlessly failed over to another VSA in the cluster.
About the author:
Cormac Hogan is a Senior Technical Marketing Manager responsible for storage in the Infrastructure Product
Marketing group at VMware. His focus is on core vSphere storage and virtual storage in general, including VSA
and other storage technologies. He was one of the first VMware employees at the EMEA headquarters in Cork,
Ireland, in April 2005. He spent two years as the Technical Support Escalation Engineer for Storage before
moving into a Support Readiness Training role, where he developed training materials and delivered training to
technical support and VMware support partners.
vMware, Inc. 3401 Hillview Avenue Palo Alto CA 94304 USA Tel 877-486-9273 Fax 650-427-5001 www .vmware .com
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