Director or core switch: which one works for you?


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SAN security and backup
Another feature more companies are asking for is security. While many of today's SANs exist in physically secure environments, the inclusion of SAN islands throughout the enterprise in could compromise this security. Hence the increased interest for switch vendors to provide secure logins, authenticated logins and requirements to encrypt data between the server and the storage.

Another technology worth watching is the inclusion of backup agents and management code by vendors such as Veritas into the FC switches. But with all of these emerging technologies, some divergences are occurring as well. One interesting divergence is the re-emergence of what SANs were originally designed for, SANs designed exclusively for backups. In most SAN environments, two paths to the storage exist so that if one path fails, the other can maintain the connectivity to the disk. However, when backups occur in the SAN environment, contention may also arise on these data paths when the backups run. This contention inhibits the free flow of data and creates performance issues for the application if it is needed at the same time the backup is running.

By creating a tertiary SAN with existing technology, it's possible to eliminate or minimize the contention issues that arise between the backups and the primary paths to direct access storage device (DASD). While creating this tertiary SAN would

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require additional FC connections for all of the servers using it and at least one more SAN switch in the infrastructure, it could help to resolve the performance problems experienced in many SAN environments today during peak backup periods.

Switch within the storage array
The other interesting divergence going largely unnoticed but that may also have an impact to the bottom line of businesses is that of the creation of the back end switch within the storage array. Vixel has taken its patented rights to the arbitrated loop switch, put it on a chip, and has started marketing a back end for SANs within the storage array between the storage controller and the disk drives. Vixel then uses its documented switch performance advantage to speed up disk performance, increase the ability of a RAID controller to manage 3X to 4X as many back-end disks-up to 120 disks as opposed to only 30 to 45 now-and lowers the cost per megabyte to the end user by 15% to 20%. Their competition in their space is essentially nil and they report an increased amount of interest in this architectural design, especially since Hewlett-Packard came to market with a storage array using this architecture in July 2002.

With the emergence and divergence of these new and existing technologies within the SAN architecture, the bar for data delivery and availability on SANs will be raised even further. While the evidence points to a convergence of existing SAN architectures for many environments, it also points to a new level of expectations and base line for functionality performance in the SAN switch infrastructure and even the storage arrays themselves. This new infrastructure will create a new SAN infrastructure, one that is simpler to manage, better performing, easier to scale and more reliable than ever before.

This was first published in November 2002

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