Introduction


IP Storage, also known as SOIP (Storage over IP), is a general term referring to the use of Internet Protocol within a Storage Area Network (SAN). IP storage is an alternative to the traditional Fiber Channel framework of the original SANs. With IP network bandwidth expanding, storage requirements growing, and the advent of iSCSI, networking and storage will merge. iSCSI is the convergence of SCSI commands for storage and IP protocols for networking. iSCSI is an end-to-end protocol for transporting storage I/O block data over an IP network. The protocol is used on servers (initiators), storage devices (targets), and protocol transfer gateway devices. iSCSI uses standard Ethernet switches and routers to move the data from server to storage. It also enables IP and Ethernet infrastructure to be used for expanding access to SAN storage and extending SAN connectivity across any distance.



Leveraging SCSI and IP for Network Storage


The figures below show how SCSI is mapped to TCP/IP through the iSCSI layer, releasing SCSI from its parallel bus structure.
Fig3-iSCSI-Protocol-Stack.jpg
Fig2-Leveraging-SCSI&IP-for-Storage-Networking.jpg

Images courtesy of http://www.soltechnology.com/


How it works

In a system supporting iSCSI, a user or software application issues a command to store or retrieve data on a SCSI storage device. The request is processed by the operating system and is converted to one or more SCSI commands that are then passed to software or to a card. The command and data are encapsulated by representing them as a serial string of bytes proceeded by iSCSI headers. The encapsulated data is then passed to a TCP/IP layer that breaks it into packets suitable for transfer over the network. If required, the encapsulated data can also be encrypted for transfer over an insecure network.
The packets are sent over the network or the Internet. At the receiving storage controller, the packets are recombined and, if necessary, decrypted into the original encapsulated SCSI commands and data. The storage controller then uses the iSCSI headers to send the SCSI control commands and data to the appropriate drive, which performs the functions that were requested by the original computer or application.

how_iSCSI_works.jpg








Image courtesy of http://www.networkworld.com/


Advantages of IP-based Storage


  • Familiar network technology and management
  • Reduces training and staff costs
  • Proven transport infrastructure
  • Increases reliability
  • Transition from 1 Gigabit Ethernet to 10-Gigabit Ethernet and Beyond
  • Protects investment with simplified performance upgrades
  • Scalability over long distances
  • Enables remote data replication and disaster recovery
  • Brings Ethernet economics to storage
  • Enables lower total cost of ownership
  • Data is centralized, so it drastically Reduces Back-Up Time (especially versus tape storage)

Security Concerns


iSCSI supports a fairly comprehensive set of security features.ACLs (Access Control Lists), the IP security protocol- IPSec, the CHAP (Challenge Handshake Authentication Protocol)and the use of VPNs (Virtual Private Networks). Most of the security problem with iSCSI and other IP Storage occur when the data center isn't following proper security protocols. The best way to secure your IP storage is to follow the best practices and new security developments.

Security Guidelines
  1. Segregate the iSCSI SAN
  2. Secure the management interfaces
  3. Disable unneeded network services
  4. Employ CHAP and other authentication wherever possible
  5. Employ IPSec or other encryption wherever necessary

Weighing Your Options


Other than security concerns, the next pressing issue with IP Storage is network performance. Although it is true that fiber channel performs better, iSCSIWhen you start storing all of your data on an existing IP network, you need to consider how much traffic your network can handle. Will your applications suffer from the increased traffic? Would it be more efficient to put the storage on its own network and isolate it from other traffic? Perhaps files that are constantly accessed might be better off being isolated to prevent an abundance of traffic which could otherwise be avoided. One way to prevent this from happening is to use both Fibre Channel and IP Technologies in tiered storage. This enables you to separate highly sensitive data from data that is only accessed every once in a while. This is the road that many of the large corporations are taking.



Who will use IP Storage

IP Storage will most likely be used within the corporate world. Small and medium-sized businesses will benefit from its reliability, cost-effectiveness, simple upgrades, and the fact that IP Storage does not require a data maintenance staff. iSCSI holds about 2-3 terabytes versus fibre channels 5 terabytes. However, iSCSI costs about $3,500-$4,500 versus f.c.'s $7,500. In 2010, when 10gb ethernet should be common, speeds will have evened out and consumers may choose iSCSI for it's ease of use.

Conclusion


For corporate environments, IP storage enables high availability of data, lower costs, familiar management areas, and gigabit performance. Using stable TCP/IP technology for storage provides an affordable solution that allows for the expansion of corporate applications without drastic changes in network infrastructure.

Related Terms

Disaster Recovery Plan
SAN
SCSI
TCP/IP
Fibre Channel
NAS
CAS

Additional Links

SearchStorage.com
iSCSIstorage.com
SNWonline.com

Resources

IP Storage Devices
IP Storage Books
HP Storage Works