R&M Data Center Handbook

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3.8.5. iSCSI & InfiniBand
Another driver of the continued development
of Ethernet is the connection of
storage resources to the server landscape
via iSCSI.
Overview of Ethernet Development
iSCSI Internet Small Computer System Interface
At the beginning, iSCSI supported speeds
of 1 Gbit/s for this purpose, which previously
was no real competition in a Fibre Channel
technology field that generally used SAN.
This is because their storage networks
allowed for connections with 4 and even 16
Gbit/s today. However, changes began
with the introduction of 10 gigabit Ethernet
(10 GbE), even in this area. (graphic)
Time scale with introduction timeframe of the technologies
This is because network managers are now increasingly toying with the idea of using Ethernet not just for their
LAN networks, but also using the same physical network to integrate their SAN traffic. Such a change not only
lowers the number of physical connections in the network, but also reduces general network complexity as well as
associated costs. This is because a separate, costly Fibre Channel network becomes unnecessary through the
use of iSCSI over Ethernet as an alternative to FCoE.
iSCSI is a method which enables the use of the SCSI protocol over TCP/IP. As in normal SCSI, there is a
controller (initiator) which directs communication. Storage devices (hard disks, tape drives, optical drives, etc.) are
called targets.
Each iSCSI node possesses a 255-byte-long name as well as an alias, and both are independent of its IP address.
In this way, a storage array can be found even it is moved to another network subsegment.
The use of iSCSI enables access to the storage network
through a virtual point-to-point connection without separate
storage devices having to be installed. Existing network
components (switches) can be used since no special new
hardware is required for the node connections, as is the
case with Fibre Channel. Access to hard disks is on a block
basis and is therefore also suitable for databases, and the
access is transparent as well, appearing at the application
level as an access to a local hard disk.
Its great advantage over a classic network is its high level of
security, since iSCSI attaches great importance to flawless
authentication and the security of iSCSI packets, which are
transported over the network encrypted. The performance
that is possible with this technology definitely lies below that
of a SCSI system that exists locally, due to the higher
latencies in the network. However, with bandwidths currently
starting at 1 Gbit/s or 125 MB/s, a large volume of data can
be stored.
InfiniBand
Since InfiniBand is scalable and supports quality of service (QoS) as well as failover (redundancy function), this
technology was originally used for the connection between HPC servers. From that time, servers and storage
systems have also been connected via InfiniBand, to speed up the data transfer process.
InfiniBand is designed as a switched I/O system and, via the I/O switch, connects separate output units, processor
nodes and I/O platforms like mass storage devices at a high data rate. The connection is carried out over a
switching fabric. The point-to-point connection operates in full-duplex mode.
Data transmission in InfiniBand is packet-oriented, and data packets have a length of 4,096 bytes. In addition to its
payload, every data packet has a header with addresses and error correction. Up to 64,000 addressable devices
are supported.
R&M Data Center Handbook V2.0 © 08/2011 Reichle & De-Massari AG Page 105 of 156