Iscsi; Iscsi Benefits; Connectivity - IBM TotalStorage DS300 Best Practices Manual

Simple to implement: Because NAS devices attach to mature, standard LAN
infrastructures, and have standard LAN addresses, they are, typically,
extremely easy to install, operate and administer. This plug and play operation
results in low risk, ease of use, and fewer operator errors, so it contributes to
a lower cost of ownership.

2.3.2 iSCSI

As mentioned in 2.1, "What Internet SCSI (iSCSI) is" on page 12, iSCSI is a
network transport protocol for SCSI that operates on top of TCP. iSCSI
encapsulates SCSI protocols into a TCP/IP frame, so that storage Controllers
can be attached to IP networks.
Application I/O request
initiates block I/O which is
encapsulated in TCP/IP and
sent to disk
Figure 2-6 iSCSI uses block I/O

2.4 iSCSI benefits

The following topics discuss a few of the benefits that come with iSCSI storage
connections.

2.4.1 Connectivity

iSCSI can be used for direct attached storage (DAS) or SAN connections. iSCSI
capable devices could be placed on an existing LAN (shared with other
applications) in a similar way to NAS devices. Also, iSCSI capable devices can
be attached to a LAN which is dedicated to storage I/O (in other words an IP
SAN), or even on a LAN connected to only one processor (like a DAS). These
options are shown in Figure 2-7 on page 22.
Application
server
IP network
Block I/O
IP protocol
iSCSI Appliance
iSCSI appliance "unwraps"
the I/O from TCP and
reads/writes block on disk
Chapter 2. iSCSI overview
21