As recently as two years ago, IT managers had two choices for networked storage: block-level storage using Fibre Channel SANs (storage area networks) or file-level storage using IP-based NAS (network-attached storage) products.
This past year, another choice has emerged with the wider availability of iSCSI storage units. Now, IP can deliver block-level storage networking to servers at a performance level that is more suitable for many applications than the file-level access that has been available from NAS products.
IP storage's ability to consolidate network storage also makes it attractive when compared with direct-attached storage units, which provide storage only for individual servers.
Furthermore, we are now seeing small and midrange storage devices that support the iSCSI protocol and NAS protocols such as CIFS (Common Internet File System) and NFS (Network File System). This will let IT managers use the protocol that makes the most sense for a particular application.
Click here for a review of a device that supports both NAS and iSCSI protocols, Adaptec's Snap Server 18000.
For example, CIFS and NFS are easy to use and facilitate data sharing among users, making the protocols attractive for basic file sharing and groupware storage. iSCSI, meanwhile, is better suited for use with application storage.
Because iSCSI and NAS can be implemented without additional networking equipment and expertise, they make IP storage an attractive solution for small and midsize businesses. And while iSCSI-based systems cannot compete with SAN solutions on sheer performance, they will be suitable for storing data for enterprise applications that are not performance-intensive, such as e-mail and small database servers.
Most applications are not designed to run off a network share, which is the way NAS devices typically present storage to servers. Application support, therefore, has been a stumbling block for IP storage, but iSCSI removes it.
iSCSI presents storage to servers as disk targets, which, from the perspective of the application, appear to be storage attached locally to the server. iSCSI works better than NAS for most applications because it provides the illusion that the networked storage being used by the server is exclusive, as opposed to a CIFS- or NFS-based network share, which is designed to allow concurrent access from multiple servers.
And because iSCSI presents storage space as virtual block-level devices, operating systems and applications have the ability to put their own file systems on them, which is something not possible with NAS.
Click here to find out why an IP-based system was the right storage consolidation and performance investment for Bayview Financial LP.
Before rolling out a major IP storage implementation, IT managers should check with their application vendors to see which types of storage are supported, as this support will have a major impact on how storage resources can be distributed.
For example, Microsoft Corp.'s SQL Server explicitly forbids the use of NAS to provide database storage. This forces IT managers to use Fibre Channel or iSCSI to provide networked storage.
Microsoft's Exchange, on the other hand, has recently been approved to work with NAS storage, provided that the NAS server is running Windows Storage Server software and that NAS devices have been tested and approved by Microsoft.
IBM's Lotus Domino server allows storage on NAS, but the product's implementation guidelines recommend using a dedicated network to shuttle data from the Domino servers to NAS devices.
Whether dealing with NAS or iSCSI, IT managers should use dedicated host bus adapters and partition out VLANs (virtual LANs) specifically for latency-sensitive applications such as databases. In cases where IT managers need to squeeze more performance out of servers, it also might make sense to add offload adapters to take the burden of TCP/IP off the server CPUs.
Click here to read more about iSCSI host bus adapters.
Although no major security issues related to iSCSI have been reported, it is safe to say that iSCSI will become a more attractive target for hackers as the protocol becomes more commonly used.
In addition to keeping performance consistent, running IP storage data on separate VLANs will help keep IP storage traffic out of reach.
IT managers also should take advantage of all the tools that have been built over the years to manage and secure IP networks. For example, a sensitive link between a server and an IP storage device can be protected using VPN technology.
The iSCSI protocol supports CHAP (Challenge Handshake Authentication Protocol), and eWEEK Labs highly recommends that IT managers use it to help ensure data security.
In addition, CHAP can help prevent users and administrators from accidentally corrupting data stored on iSCSI targets.
Existing IP tools also can be used for performance management.
Quality-of-service tools, for example, can be used to ensure that storage data never has to wait while making its way through the network, and IP traffic monitoring tools can be used to obtain trend analysis data on performance, which can be of help in planning network upgrades.
Another important benefit that iSCSI brings to the world of IP storage is that it works well over WAN links (unlike NAS protocols). This gives IT managers another option for the mirroring of data over the WAN besides protocols such as FCIP (Fibre Channel over IP), which have been used in the past to extend the reach of Fibre Channel SANs.
Senior Analyst Henry Baltazar can be reached at henry_baltazar@ziffdavis.com.
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