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When setting up a new system, one of the main considerations is, if a dedicated storage
area network should be implemented. The following possibilities are available:
Table 11.1
Method
Ethernet
Ethernet dedi-
cated to stor-
age.
NPIV
Typically, a 1 Gbit/s Ethernet device will be able to fully utilize a typical hard disk or
storage system. When using very fast storage systems, such an Ethernet device will
probably limit the speed of the system.
11.2 Xen HA with Local Storage
For space or budget reasons, it may be necessary to rely on storage that is local to the
Xen host systems. To still maintain the possibility of live migrations, it is necessary to
build block devices that are mirrored to both Xen hosts. The software that allows this
is called Distributed Replicated Block Device (DRBD).
If a system that uses DRBD to mirror the block devices or files between two Xen hosts
should be set up, both hosts should use the identical hardware. If one of the hosts has
slower hard disks, both hosts will suffer from this limitation.
96
Virtualization with Xen
Xen Remote Storage
Complexi-
Comments
ty
low
Note, that all block device traffic goes over the same
Ethernet interface as the network traffic. This may
be limiting the performance of the guest.
medium
Running the storage traffic over a dedicated Ethernet
interface may eliminate a bottleneck on the server
side. However, planning your own network with your
own IP address range and possibly a VLAN dedicated
to storage needs some more considerations.
high
NPIV is a method to virtualize fibre channel connec-
tions. This is available with adapters that support a
data rate of at least 4 Gbit/s and allows the setup of
complex storage systems.
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