iSCSI throws up many SAN implementation options

At the risk of beating a dead horse, I want to finish this series of articles on iSCSI with one thought: Be aware.

At the beginning of this series, I discussed how two customers are gaining value from their iSCSI storage-area network (SAN) implementations today. One company is using a native iSCSI disk hooked into their 100Base-T LAN and utilizing the free iSCSI software drivers offered by their storage provider. The other is using iSCSI as a Fibre Channel SAN-to-WAN bridging technology. SANs created using the iSCSI protocol on Ethernet will bring customers the value of consolidated, centrally managed storage.

The fact is that with iSCSI customers have many options in how they implement their SAN. These options range from very simple to very complex. An iSCSI SAN can be created as simply as loading a driver on your server, attach a native iSCSI disk, such as the IBM 200i, to the network, configure the disk and you're ready to go. However, every option brings with it a decision. These decisions will determine the performance, reliability, manageability and certainly the cost of your iSCSI SAN.

Enterprise Management Associates' research has shown that the primary barrier to the adoption of IP storage is the perception that the performance is poor. As I have stated in the previous articles, performance can be purchased; it is one of the many options available with iSCSI SANs. However, the benefits of an iSCSI SAN - the consolidated storage and storage management - are realized with even the lowest performing and inexpensive implementations.

This perception about performance is one reason I advocate the creation of a separate storage network. It is a simple way to shield your iSCSI SAN from problems caused by network congestion on the LAN. By separate, I do not mean exclusive but rather by creating a subnet of the LAN for your storage traffic much of the congestion problems can be eliminated while retaining centralized network management.

Another option, which was brought up by a reader, is to create virtual LANs (VLAN) for storage within the current LAN infrastructure. If your company has VLAN capabilities or is willing to purchase them, this is also a viable option for routing storage traffic to maximize the level at which the data moves through the network.

The way you build your iSCSI SAN, the options you choose and the decisions you make will affect the performance and reliability of your data access. This is why it is important to be aware of the options available to you and how these choices determine application performance. ISCSI performance is not inherently slow, however poor choices can lead to disappointing results.

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