Storage Management Strategies for the CIO
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Connectivity
Connectivity represents one of the primary benchmarks that some organizations still use to differentiate between high-end and midrange storage arrays. Simply put, many storage managers' rule of thumb is "if it supports FICON and/or ESCON connectivity, it's a high-end storage array, and if it only supports FC, it's a midrange storage array."
For shops that require either FICON or ESCON connectivity to the mainframe, six companies--EMC, Hewlett-Packard Co., HDS, IBM, StorageTek and Sun Microsystems Inc.--currently offer that functionality on their traditional monolithic boxes. EMC's new DMX800 breaks some new ground on this front in that they now offer FICON connectivity on a modular array.
Storage arrays also must support FC in some capacity to be considered high-end. Some newer companies such as EqualLogic, in Nashua, NH, hope to gain market share exclusively using an iSCSI interface in its PeerStorage Array 100E, but it seems unlikely that tactic will work at this early stage of the IP storage game. More likely, companies such as Network Appliance Inc.--which recently added 2Gb FC connectivity on their FAS900c series arrays--will have more success in gaining the status of high-end in the minds of users.
With vendors such as Microsoft Corp. and Novell Inc. already offering a standards-compliant iSCSI driver for their respective operating systems, and EMC joining Network Appliance in the fray, it seems that iSCSI will become a requirement sometime in the near future for some high-end array implementations. The two types of applications most likely to need iSCSI initially are low-cost servers that organizations are looking to connect to IP SANs, and those applications that need data stored at a remote site, but need a less costly way to connect the two sites.
The other looming connectivity requirement is 4Gb/s FC. Recently, the Fibre Channel Industry Association extended it from an intracabinet storage device interconnect to switched SAN fabrics, so it will likely find its way into arrays as an option. FC at 4Gb/s will make the most sense for those applications that are performance intensive, but cost-sensitive, where you can't justify upgrading the entire enterprise to meet one applications requirements. New host bus adapters (HBAs) can utilize the existing infrastructure and be backwards compatible with the 1Gb and 2Gb FC protocols.
Capacity
Capacity comes in as the final feature traditionally associated with monolithic high-end arrays. Many of today's putative midrange arrays now support larger configurations of raw capacity than the latest monolithic arrays. For instance, 3PAR's latest InServ S800 supports up to 2,560 147GB drives with a maximum raw capacity of nearly 380TB, which more than doubles the number of disk drives and raw capacity that the HDS 9980 V will support.
Be careful about interpreting capacity. If your application just calls for large amounts of raw capacity with no special needs for performance, availability, reliability or connectivity, an array that's simply large may be just what you need. But usually, one factor alone rarely holds that much weight in the decision-making process.
Price
With a midrange system configured with 2TB of storage coming in around $40,000 to $60,000 and a similarly configured monolithic array coming in between $120,000 and $200,000, you may wonder why you would pay the premium for a monolithic array.
You can't answer that question without considering the application. For applications that can never afford downtime and where the penalties are huge in terms of lost revenue, why risk the cost to the bottom line and the perception problem you create with the client? In that case, spending 8 cents/MB for a traditional monolithic high-end array is cheap compared to the consequences.
Because of arguments like this, many storage managers forego midrange arrays in favor of more expensive boxes. Jim Tuckwell, IBM's product marketing manager, says IBM has seen about a 50-50 split in their customer environments where price point is cited as the reason for the choice they made. Some organizations gain an economic advantage by standardizing on high-end monolithic storage arrays, while others take advantage of the attractive price point of midrange storage arrays.
This last example illustrates that much more goes into making a decision about which high-end storage array to buy than just one variable. Yet with all of the variances within these first six present, the factors of serviceability and manageability may be the ones that ultimately sway purchasing decisions in the future.
This was first published in September 2003
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