HBAs Give iSCSI Performance More Gusto

iSCSI HBAs let IT managers squeeze more performance out of servers and storage units.

iSCSI HBAs let IT managers squeeze more performance out of servers and storage units.

High performance is not a hallmark of the iSCSI protocol, but iSCSI host bus adapters release server CPUs from the burden of network processing. The CPU cycles that are saved can be used for applications.

In most iSCSI implementations, a standard software initiator is used to provide iSCSI connectivity from servers to iSCSI storage devices. iSCSI initiator software is free, so it allows IT managers to implement iSCSI storage without added acquisition costs.

However, the main drawback to iSCSI software initiators is that they can burn large amounts of CPU resources, depending on the environment in which they are used. When used in high-transaction environments, for example, a software initiator can consume as much as 35 percent of a servers processing power. This can cause application performance degradation, especially if a server has only one or two processors.

By implementing iSCSI HBAs, which are available from vendors including QLogic Corp. and Alacritech Inc., IT managers can conserve precious CPU cycles and delay costly server upgrades.

At a cost of about $600 per adapter, iSCSI HBAs are not inexpensive, but the cost of adding them will still be far less than implementing Fibre Channel SANs (storage area networks) or rolling out new servers to gain processing power.

iSCSI adapters differ from standard Ethernet adapters in that they have built-in processors to handle TCP/IP networking chores (which eat up most of the CPU cycles) and manage the iSCSI protocol itself.

eWEEK Labs also expects that iSCSI HBAs will facilitate diskless server environments in the future. Because iSCSI initiator software is embedded in an iSCSI HBA, a diskless client booting up the HBA can quickly locate and log in to the iSCSI target storing the operating system and applications for that diskless client.

This isnt possible with standard iSCSI initiator software now because that software has to ride on top of a server operating system to function.

As diskless server technology matures, we expect to see it implemented in blade servers. The resulting removal of local hard drives will greatly simplify cooling issues for blades and allow blade vendors to gain higher densities than are possible today.


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