The project team on the SAN tests (from top to bottom):

Dipl.-Ing. Horst Köhler
(Group Leader IT System Planning, IT Platform Intelligent Storage at DeTeCSM Darmstadt),

Dipl.-Ing. (FH) Dirk Kabelitz
(Group Leader Client/Server System Management at DeTeCSM Magdeburg),

Ronald Löbig
(Systems Engineer with COMPAREX).

Is SAN A Viable Option for Data Centres?

As volumes of data continue to grow, data centre operations need Fibre Channel technology more than ever to manage their data flow efficiently. The heterogeneity of today's IT urgently requires a SAN solution. Many vendors have their individual solutions, but vendor-independent system integration labs are still a rarity - reason enough for Deutsche Telekom subsidiary DeTeCSM (Computer Service Management GmbH) to create a complex test scenario at its own location in Magdeburg to achieve "meaningful results for the further implementation of SANs in its data centres".

Test Scenario: Spotlight on Connectivity and Performance

DeTeCSM selected COMPAREX to provide the support and consultancy required to conduct its extensive tests, carried out between October 1999 and January 2000, because of COMPAREX`s comprehensive expertise in the area of enterprise storage in general and its success in implementing SAN solutions in particular. The tests used the configuration already existing at DeTeCSM installed by COMPAREX (with the exception of the HPUX servers). The aim was not only to test the performance of individual components against each other, but also to test the overall system within the framework of a comprehensive Storage Area Network. The IT environment listed below provided the basis for testing:

• Operating systems: Windows NT 4.0, SUN SOLARIS 2.6, HP-UX 11.0, (AIX was considered as a further theoretical component)
• Hardware (servers): Siemens, Compaq, SUN, HP
• Hardware (SAN components): COMPAREX, FC Switch ED5000 (McData), HP-FC-Switch F16 (Brocade with HP firmware), COMPAREX-FC-SCSI bridge CB 1200
• Hardware (disk subsystems): COMPAREX TETRAGON 2100, EMC 3930.

The test used standard benchmarking software. Particular emphasis was placed on analysing the difference in performance between existing point-to-point solutions and the new switched topology.

Results

DeTeCSM anticipated a considerable downgrade in performance after moving to a switched topology. However, Dirk Kabelitz had this to say about the test results: "After moving to a switched fabric SAN, the performance losses resulting from connecting to a switch are only around 1% compared with our existing point-to-point connections. These are absolutely superb results!."

Test Scenarios:

• Direct connection of server to disk subsystem via Fibre Channel using an Arbitrated Loop Protocol
• Connection of server to disk subsystem via Fibre Channel switch (Fabric Protocol)
• Connection of server to disk subsystem via Fibre Channel switch with two FC connections and with load balancing software
• Connection of a cluster (without SUN) to disk subsystem via Fibre Channel switch with two FC connections (high availability tests)
• Dedicated assignment of LUNs for the various operating systems (heterogeneity tests)
• Zoning via FC switch with simultaneous connections to two disk subsystems (COMPAREX, EMC)
• A maximum bandwidth per server port of 70 to 85 MB/s was measured in read-only mode and 15 to 20 MB/s in read/write mode (70:30 ratio)

The individual tests in the above scenarios produced extremely positive results.

Conclusions: SAN Works Well!

"What we have seen", states Dirk Kabelitz, "is that Storage Area Networks function perfectly at a physical level and that integration into operating systems has already been implemented, at least in part (HP-UX runs in Arbitrated Loop mode only). However, there are still some problems to overcome as some manufacturers are still struggling with drivers. Having said that, they are in the process of designing and implementing solutions which will soon be available." Comprehensive SAN management, however, is currently still in its infancy.

Assessment: SAN Implementation to Progress Rapidly

"In conclusion," sums up Dirk Kabelitz, "we can say that Storage Area Networking is a fast developing technology. First products are now on the market and the manufacturers have started to unite to work towards creating uniform standards, enabling those solutions the customer needs to be implemented."

SANs (in FC-AL mode) have already been implemented within the organisation. DeTeCSM has implemented them to replace backups across the network and to consolidate storage. COMPAREX has demonstrated that it is a competent and ideal partner for the future as far as enterprise-wide Storage Area Networking is concerned. Says Dirk Kabelitz: "As a result of our tests we will now certainly continue to extend our Storage Area Network". And equally important, SAN provides for independent storage management and can easily absorb annual data growth rates of 100%. Further tests on load balancing, SAN management and switch cascading are planned.