A data center is a logical
entity that defines the set of resources used in a specific environment. A data
center is considered a container resource, in that it is comprised of logical
resources, in the form of clusters and hosts; network resources, in the form of
logical networks and physical NICs; and storage resources, in the form of
storage domains.
A data center can contain
multiple clusters, which can contain multiple hosts; it can have multiple
storage domains associated to it; and it can support multiple virtual machines
on each of its hosts. A Red Hat Enterprise Virtualization environment can
contain multiple data centers; the data center infrastructure allows you to
keep these centers separate.
All data centers are
managed from the single Administration Portal.
Red Hat Enterprise
Virtualization creates a default data center during installation. It is
recommended that you do not remove the default data center; instead, set up new
appropriately named data centers
The Storage Pool Manager
The Storage Pool Manager
(SPM) is a role given to one of the hosts in the data center enabling it to
manage the storage domains of the data center. The SPM entity can be run on any
host in the data center; the Red Hat Enterprise Virtualization Manager grants
the role to one of the hosts. The SPM does not preclude the host from its
standard operation; a host running as SPM can still host virtual resources.
The SPM entity controls
access to storage by coordinating the metadata across the storage domains. This
includes creating, deleting, and manipulating virtual disks (images),
snapshots, and templates, and allocating storage for sparse block devices (on
SAN). This is an exclusive responsibility: only one host can be the SPM in the
data center at one time to ensure metadata integrity.
The Red Hat Enterprise
Virtualization Manager ensures that the SPM is always available. The Manager
moves the SPM role to a different host if the SPM host encounters problems
accessing the storage. When the SPM starts, it ensures that it is the only host
granted the role; therefore it will acquire a storage-centric lease. This
process can take some time.
SPM Priority
The SPM role uses some of a
host's available resources. The SPM priority setting of a host alters the
likelihood of the host being assigned the SPM role: a host with high SPM
priority will be assigned the SPM role before a host with low SPM priority.
Critical virtual machines on hosts with low SPM priority will not have to
contend with SPM operations for host resources.
You can change a host's SPM
priority by editing the host.
Using the Events Tab to Identify Problem Objects in Data Centers
The Events tab
for a data center displays all events associated with that data center; events
include audits, warnings, and errors. The information displayed in the results
list will enable you to identify problem objects in your Red Hat Enterprise
Virtualization environment.
The Events results
list has two views: Basic and Advanced. Basic view displays the event icon, the
time of the event, and the description of the events. Advanced view displays
these also and includes, where applicable, the event ID; the associated user,
host, virtual machine, template, data center, storage, and cluster; the Gluster
volume, and the correlation ID.