Owner's manual

Important concepts
To understand the configuration of the backup net work and how it fits into the local-area net work (LAN ),
review the following sections.
Internet SCSI (iSCSI) protocol
Internet SCSI (iSCSI) is a standard protocol for universal access to shared storage devices over standard,
Ethernet-based transmission control protocol/Internet protocol (TCP/IP) networks. The connection-oriented
protocol transports SCSI comm a nds, data, and status across an I P net work.
The iSCSI architecture is based on a client-server model. The client is a host system that issues requests
to
read or write data. iSCSI refers to a client as an initiator. The server is a resource that receives and
ex ecutes client requests. iSCSI refers to a server as a target.
File ser vers, which store the programs and data files shared by users, normally play the role of server.
With the VLS, the application and backup servers within your network act as clients or initiators and
the
VLS acts as a ser ver or target. The initiators can either be iSCSI software simulation or host bus
adapters (H BAs) on the server that is being backed up.
Disk-to-Disk-to-Tape (D2D2T) backup capabilities
TheVLS is astorage resource used by asinglebackupserver orsharedby multiplebackupservers using
an Ethernet network. By using standard backup software, you can copy backup data that resides on the
VLS to physical tape for long-term data retention.
The following illustration shows application servers sending backup data over a Gigabit Ethernet (G bE)
L AN to backup servers sharing VLS D2D storage over GbE.
NOTE:
The con
nection from the Client — Tape can be either FC or direct attached SCSI.
Clients
Ethernet
VLS 1000i Client Client - Tape
Figure 1 Disk-to-Disk-to-Tape backup
In addition to being part of the L A N, the backup servers, and the V LS are par t of the GbE ba ckup L A N.
Redundant Array of Independent Disks (RAID)
RAID provides convenient, low-cost, reliable storage by saving da ta on more than one disk drive
simultaneously. If one disk drive in a RAID 5 configuration becomes unavailable, the others continue to
work in a degraded state, thus avoiding downtime for users.
16
Introduction