IP SAN or Fibre Channel SAN?
Fibre Channel SAN topology is the high-speed storage option at a top-dollar price. And until recently, a Fibre Channel SAN was the only option for networked storage. But with the advent of iSCSI, companies now have another SAN topology, called an IP SAN, which is more cost-effective than Fibre Channel. Though an IP SAN offers slower throughput than a Fibre Channel SAN, dedicated IP SANs running iSCSI are positioned to be the practical and economical alternative for many storage environments.
So, which storage topology is optimal for an MS-Exchange Server environment? Based purely on speed, one would expect the Fibre Channel SAN to outperform an IP SAN, but other factors must be considered. As with any environment, the storage device, the interface connection, the switches, and even the server, must all be accounted for in the system. Any one bottleneck can strangle the entire network, eliminating any benefit a high-performance network has to offer.
To help decide which topology is best for MS-Exchange Server and uncover any potential bottlenecks, Spectra Logic set out to compare the performance of a Fibre Channel and Gigabit Ethernet in the same environment. The intent of this benchmark comparison test was to discover the benefits and drawbacks of choosing a Fibre Channel SAN versus an IP SAN, considering total cost and overall performance.
The iSCSI protocol runs SCSI on a TCP/IP network. Widespread experience and familiarity with 1P networks facilitate easy deployment of such technology. The total cost of switches, cabling and Host Bus Adapters (HBAs) is an important consideration. Common list prices of components (as of May 2003) illustrate the magnitude of cost differences for IP SAN and fibre SAN topologies (see Table 1).
Overall, components for iSCSI are considerably less expensive than Fibre Channel components, especially considering the absolute minimum price range. Fibre Channel is the higher-performing technology, but it is expensive, more complex, and requires Fibre Channel expertise.
Performance: The Environment
Microsoft's MS-Exchange Server is an extremely popular application for e-mail, workgroup scheduling and common office communications. It is used extensively in both large and small firms, and runs on a wide variety of hardware. For the benchmark test, a 20GB database was created to represent four separate mailboxes. The host was an Intel Pentium 4 dual-processor (2 x 2.0GHz) server with four 7200-RPM ATA disk drives.
The database was backed up to a Spectra Logic Spectra 20K tape library. Four Sony AIT-3 tape drives were used and both tests were run to a single drive, two drives, three drives, and all four drives to see how each configuration would scale and to reveal any bottlenecks (see Table 2).
The same server, data, library and tape drives were used for both storage network configurations. Only the network and host connectivity was changed. Figure 1 shows the configurations that were tested.
The benchmark test was performed to compare the throughput performance between Fibre Channel and iSCSI while backing up a 20GB MS-Exchange Sever database. The more costly SAN Fibre Channel connectivity was expected to significantly outperform iSCSI over Gigabit Ethernet.
The Performance Data
The complete test results show an unexpectedly small throughput performance differential between the two network configurations (see Table 3).
While the Fibre Channel did produce slightly higher throughput speed, iSCSI provided very competitive results. The test concluded that the high-speed throughput of a Fibre Channel SAN was limited by a significant performance bottleneck within the system. A significantly faster server might produce a wider differential, but similar MS-Exchange Server environments will probably see similar results.
Fibre Channel offers impressive throughput, and where performance is imperative, a Fibre Channel SAN is an excellent choice. However, IP SAN equipment is less expensive; the topology is more familiar to data center staff, and it is conducive to running other applications over the network.
Given the equal performance with an expected 63-74% cost advantage, an IP SAN using iSCSI should quickly become the backup consolidation network of choice for MS-Exchange Server. In fact, iSCSI should be considered when choosing any storage environment, especially ones with performance constraints similar to those of mail servers.
Users upgrading from a typical DAS environment should consider an IP SAN as a familiar and practical alternative to a Fibre Channel SAN. As this benchmark comparison illustrates, any backup is only as fast as its slowest link. A database, backplane, disk or server might not be able to achieve the faster throughputs that justify a high-performance Fibre Channel SAN.
Spectra Logic manufactures, sells, and supports both native Fibre Channel and Gigabit Ethernet tape libraries. Each has its advantages. But an IP SAN will provide solid performance in many environments, free backup traffic from the LAN, and allow other IP traffic if needed--at a cost--effective deployment price.
Table 1 Component Fibre List iSCI Price iSCSI Minimum Price of of Tested Price Tested HBA $1,000 $400 $400 Driver (included Free with Linux, Free with Linux, with HBA) Windows, Novell, Windows, Novell, NetApp and HP-UX NetApp and HP-UX Switch (per port) $1,000 $70-250 $0 Network Interface Card (NIC) N/A $50-100 $0 TOTAL $2,000 $520-750 $400 Savings on IP SAN 63-74% 80% Table 2 Component Fibre Channel iSCSI Server 2x2.0 GHz Pentium 4, 2x2.0 GHz Pentium 4, 7200 RPM ATA Disk Drives 7200 RPM ATA Disk Drives RDBMS MS-Exchange Server 2000 MS-Exchange Server 2000 DB Size 20 GB 20 GB Switch Brocade Silkworm 3200, Extreme Summit version 3.02 5i IP Switch Host Bus Adaptor Qlogic QLA-2200 (FC) Intel PRO/1000 T IP (iSCSI), version 1 Backup Software Veritas Backup Exec, Veritas Backup Exec, version 9.0 version 9.0 Backup Hardware Spectra 20k, 4 AIT-3 Spectra 20k, 4 AIT-3 tape drives tape drives (1 Gb Fire Channel, (1 Gb Fire Channel, using a G1 F-QIP) using a G1 F-QIP) Table 3 Backup Fibre Channel ISCSI Single stream 19.32 MB/Sec 21.14 MB/Sec Two stream 32.06 MB/Sec 24.82 MB/Sec Three stream 35.24 MB/Sec 33.72 MB/Sec Four stream 35.35 MB/Sec 32.72 MB/Sec
Sharon Isaacson is senior product manager and Colman Sanchez is technical writer at Spectra Logic ((Boulder, CO)
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|Title Annotation:||Storage Management|
|Publication:||Computer Technology Review|
|Date:||Aug 1, 2003|
|Previous Article:||Information Lifecycle Management.|
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