What iSCSI brings to tape

Computer Technology Review, March, 2004 by Stephen Mak

iSCSI, an Internet Engineering Task Force standard, breathes fresh air into the world of data protection. Providing access of storage devices (e.g., tape libraries and disk arrays) over IP, iSCSI products help make backup and archive easy and affordable, enable new data protection applications and deliver high backup performance. iSCSI is a great backup technology and IT professionals should seriously consider using it in tape environments.

Easy Backup

iSCSI technology makes backup easy. iSCSI products are easy to connect, and iSCSI networks are simple to manage. With Microsoft's certifications, iSCSI products are guaranteed to work in Windows environments. iSCSI products are connected to Ethernet networks, which are as familiar as telephone connections. Connecting an iSCSI host to an iSCSI storage device is as simple as hooking up a phone jack. Plus, most IT departments already have Ethernet LANs. iSCSI enables the user to employ the same technology to build storage networks. Users can manage iSCSI using familiar LAN management tools while taking advantage of their existing IP networking knowledge. In other words, the learning curve of SCSI is minimal, as is network management cost.

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In November 2003, Microsoft certified products from 14 storage hardware makers for use with Windows under the "Designed for Windows Logo Program." This certification insures plug-and-play operations for the products with Windows systems and provides users a broader choice of iSCSI hardware components proven to run Windows and Microsoft's iSCSI architecture. Microsoft's endorsement further strengthens iSCSI's role in storage networking.

iSCSI networks offer an effective, affordable and familiar route to storage consolidation. The user can establish a single data protection policy for the organization and enforce the policy through a centralized backup operation. This centralized backup scheme allows the user to add library and networking resources (independent of the servers) to handle network failures and to cope with increased backup data volumes. Backup performance is also greatly improved because storage applications and user applications do not share networks. This kind of centralized data protection scheme, along with the option to scale and add redundancy, offers users greater control over their backup operations, increases their productivity in managing data and simplifies data protection.

New Applications

iSCSI expands data protection. With IP networking capability, the user can back up data remotely on systems without direct access to a tape library. Ethernet links run up to 100 meters on Category 5 cables and can be extended with an Ethernet switch or hub. This distance allows the user to access data between buildings. Still, many systems are typically not protected, such as server blades, desktops and laptops. For example, they may not have networking equipment and software to access a tape library. iSCSI offers these users a solution. With fast Ethernet connectivity to almost every desktop, either the user or the system administrator can backup his or her system to a tape library on the network. iSCSI tape libraries can be conveniently located next to a network printer where the user can easily change tapes. Alternatively, the tape library can be located in a server room where the system administrator can schedule remote backup jobs and change tapes without leaving the room. Presented as a network-based service and supporting remote access, iSCSI libraries provide IT professionals with new tools to expand their data protection coverage.

High Performance

iSCSI products deliver impressive numbers in backup and retrieval operations. An iSCSI host can keep a super tape drive running at full speed on a Gigabit Ethernet connection and across multiple switches. In testing, a 1.8GHz Pentium system with the Linux iSCSI software initiator sustained at 47 MB/s and used 50% CPU. This performance is enough to stream an IBM LTO2 tape drive. In fact, iSCSI performance is expected to continue to improve with processor advancements. Software initiators run on a standard Ethernet Network Interface Card (NIC) that comes with the server or desktop. Likewise, systems with hardware-based iSCSI initiators are equally impressive performing at wire speed (i.e., 80 to 90MB/s), capable of streaming two super drives on a Gigabit Ethernet connection. Hardware initiator cards offload TCP/IP processing, thereby reducing CPU consumption. Although switching delay could affect backup performance when accessing data across multiple switches, Gigabit Ethernet switches are fast, with a maximum delay of 144 microseconds. This is the time the switch takes to receive a jumbo frame packet (i.e., 9000 bytes) on an incoming port, and forward it onto an outgoing port. At this rate, an iSCSI host can send data to an iSCSI tape library across two to three switches without significant performance degradation. iSCSI products and Gigabit Ethernet switches make remote backups possible and deliver the performance that the user needs for backup and archive operations.