HPP Enterprises P4000 SAN - Manual (Page 7)

7
storage or from storage to storage. Each host acts as an initiator (iSCSI client) connecting to a storage
target (HP StorageWorks P4000 SAN volume) in a SR, where the data is stored.
Since SCSI commands are encapsulated within an Ethernet packet, storage no longer needs to be
locally-connected, inside a server. Thus, storage performance for a XenServer host becomes a function
of bandwidth, based on 1 Gb/second or 10 Gb/second Ethernet connectivity.
Moving storage from physical servers allows you to create a SAN where servers must now remotely
access shared storage. The mechanism for accessing this shared storage is iSCSI, in much the same
way as other block-based storage protocols such as Fibre Channel (FC). SAN topology can be
deployed efficiently using the standard, pre-existing Ethernet switching infrastructure.
Benefits of shared storage
The benefits of sharing storage include:
 The ability to provide equal access to shared storage is a basic requirement for hosts deployed in a
resource pool, enabling XenServer functionality such as HA and XenMotion, which supports the
migration of VMs between resource pools in the event of a failover or a manual live state.
 Since storage resources are no longer dedicated to a particular physical server, utilization is
enhanced; moreover, you are now able to consolidate data.
 Storage reallocation can be achieved without cabling changes.
In much the same way that XenServer can be used to efficiently virtualize server resources, HP
StorageWorks P4000 SANs can be used to virtualize and consolidate storage resources while
extending storage functionality. Backup and DR are also simplified and enhanced by the ability to
move VM data anywhere an Ethernet packet can travel.
Storage node
The storage node is the basic building block of an HP StorageWorks P4000 SAN and includes the
following components:
 CPU
 Disk drives
 RAID controller
 Memory
 Cache
 Multiple network interfaces
These components work in concert to respond to storage read and write requests from an iSCSI client.
The RAID controller supports a range of RAID types for the node’s disk drives, allowing you to
configure different levels of fault-tolerance and performance within the node. For example, RAID 10
maximizes throughput and redundancy, RAID 6 can compensate for dual disk drive faults while better
utilizing capacity, and RAID 5 provides minimal redundancy but maximizes capacity utilization.
Network interfaces can be used to provide fault tolerance or may be aggregated to provide
additional bandwidth. 1 Gb/second and 10 Gb/second interfaces are supported.
CPU, memory, and cache work together to respond to iSCSI requests for reading or writing data.
All physical storage node components described above are virtualized, becoming a building block
for an HP StorageWorks P4000 SAN.