Servers

Each of the different server platforms (IBMEserver zSeries®, UNIX, AIX®, HP, Sun, Linux, and others), OS/400®, and Windows (PC Servers) have

implemented SAN solutions using various interconnects and storage technologies. The following sections review these solutions and the different implementations on each of the platforms.

Mainframe servers

In simple terms, a mainframe is a single, monolithic and possibly multi-processor high-performance computer system. Apart from the fact that IT evolution has been pointing toward a more distributed and loosely coupled infrastructure, mainframes still play an important role on businesses that depend on massive storage capabilities.

The IBMEserver zSeries (formerly known as S/390®) is a processor(s) and operating system mainframe set. Historically, zSeries servers have supported many different operating systems, such as z/OS, OS/390®, VM, VSE, and TPF, which have been enhanced over the years. The processor to storage device interconnection has also evolved from a bus and tag interface to ESCON channels, and now to FICON channels. Figure 2-3 on page 22 shows the various processor-to-storage interfaces.

Figure 2-3 Processor-to-storage interface connections

Due to architectural differences, and extremely strict data integrity and

management requirements, the implementation of FICON has been somewhat behind that of FCP on open systems. However, at the time of writing, FICON has now caught up with FCP SANs, and they coexist quite amicably.

For the latest news on zSeries TotalStorage products, refer to:

http://www-1.ibm.com/servers/storage/product/products_zseries.html

For the latest news on zSeries FICON connectivity, refer to:

http://www-1.ibm.com/servers/eserver/zseries/connectivity/

In addition to FICON for traditional zSeries operating systems, IBM has standard Fibre Channel adapters for use with zSeries servers that can implement Linux®.

UNIX-based servers

Originally designed for high-performance computer systems, such as

mainframes, the UNIX operating systems is today present on a great variety of hardware platforms, ranging from Linux-based PCs to dedicated large-scale

Tapes microprocessor bus OEMI Channel ESCON Channel

Bus&Tag cables

Processor

(ESCON = Enterprise Systems Connection) (FICON = Fibre Connection)

(OEMI = Original Equipment Manufacturer's Interface) FICON /

Fibre Channel

Disks and Tapes

Disks

Disks FC switch

ESCON Director

Chapter 2. How, and why, can we use a SAN? 23 stations. Due to its popularity and maturity, it also plays an important role on both existing and legacy IT infrastructures.

The IBMEserver pSeries® line of servers, running a UNIX operating system called AIX, offers various processor to storage interfaces, including SCSI, SSA, and Fibre Channel. The SSA interconnection has primarily been used for disk storage. Fibre Channel adapters are able to connect to tape and disk. Figure 2-4 shows the various processor-to-storage interconnect options for the pSeries family.

Figure 2-4 pSeries processor-to-storage interconnections

The various UNIX system vendors in the market deploy different variants of the UNIX operating system, each having some unique enhancements, and often supporting different file systems such as the Journal File System (JFS),

Enhanced Journal File System (JFS2), and the Andrew File System (AFS®). The server-to-storage interconnect is similar to pSeries, as shown in Figure 2-4. For the latest news on pSeries TotalStorage products, refer to:

http://www-1.ibm.com/servers/storage/product/products_pseries.html

Windows-based servers

Based on the reports of various analysts regarding growth in the Windows server market (both in the number and size of Windows servers), Windows will become

microprocessor

Processor

bus SSA Adapter SCSI Adapter

SCSI bus

FC Adapter

loop

Disk & Tape Drives

Disk Drives

FC Switch / hub

the largest market for SAN solution deployment. More and more Windows servers will host mission-critical applications that will benefit from SAN solutions, such as disk and tape pooling, tape sharing, multipathing, and remote copy. The processor-to-storage interfaces on xSeries® servers (IBM Intel®-based processors that support the Microsoft® Windows operating system) are similar to those supported on UNIX servers, including SCSI and Fibre Channel.

For more information, see the xSeries SAN Web site at:

http://www-1.ibm.com/servers/storage/product/products_xseries.html

Other servers

The iSeries™ system architecture is defined by a high-level machine interface, referred to as Technology Independent Machine Interface (TIMI), which isolates applications (and much of the operating system) from the actual underlying systems hardware.

The main processor and the I/O processors are linked using a system bus, including Systems Product Division (SPD), and also Peripheral Component Interconnect (PCI). Figure 2-5 summarizes the various modules of an iSeries hardware architecture.

Figure 2-5 iSeries hardware design

Several architectural features of the iSeries server distinguish this system from other machines in the industry. These features include:

B

U

S

DASD TAPE COMM W/S I/O Processor RAID Wireless Ethernet Fax Special Function OP's NT Novell Application Servers Main Processor Memory Service Processor

Chapter 2. How, and why, can we use a SAN? 25

򐂰 Technology Independent Machine Interface

򐂰 Object-based systems design

򐂰 Single-level storage

򐂰 Integration of application programs into the operating system For the latest news on iSeries TotalStorage products, refer to:

http://www-1.ibm.com/servers/storage/product/products_iseries.html

Single-level storage

Single-level storage (SLS) is probably the most significant differentiator in a SAN solution implementation on an iSeries server, as compared to other systems such as z/OS, UNIX, and Windows. In OS/400, both the main storage (memory) and the secondary storage (disks) are treated as a very large virtual address space known as SLS.

Figure 2-6 compares the OS/400 SLS addressing with the way Windows or UNIX systems work, using the processor local storage. With 32-bit addressing, each process (job) has 4 GB of addressable memory. With 64-bit SLS addressing, over 18 million terabytes (18 exabytes) of addressable storage is possible. Because a single page table maps all virtual addresses to physical addresses, task switching is very efficient. SLS further eliminates the need for address translation, thus speeding up data access.

Figure 2-6 OS/400 versus NT or UNIX storage addressing

iSeries SAN support has rapidly expanded, and iSeries servers now support attachment to switched fabrics, and to most of IBM SAN-attached storage products.

For more information, see the iSeries SAN Web site:

http://www.ibm.com/servers/eserver/iseries/hardware/storage/san.html 18,000,000 TB OS/400 NT or UNIX job 1 4GB job 3 4GB job 2 4GB job 1 job 2 job 3

In document Introduction to Storage Area Networks (Page 43-48)