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The case for high-end arrays

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The software gap is narrowing, too

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One of the best features of high-end arrays is software. Features such as the ability to synchronously or asynchronously mirror storage between arrays, create point-in-time copies and do remote copies between large distances were what separated monolithic arrays from their competitors.

Yet a number of competitors in the midrange market now offer similar functionality which has helped to erode the original value proposition of these offerings. 3PAR, in Fremont, CA, offers their InForm Operating System, which includes point-in-time copies with configurable parameters as well as remote copy functionality. Network Appliance's Data ONTAP operating system also offers similar snapshot and mirroring functionalities as well as a snap restore capability that allows a system to revert back to a specified point in time.

In response to this, the traditional providers of monolithic arrays have found new ways to add value in their native software. IBM now offers advanced functions for use in conjunction with their zSeries servers such as priority I/O queuing and multiple allegiance on its ESS Model 800. Priority I/O queuing ensures important applications have priority access to storage resources, while multiple allegiance enables different operating systems to perform multiple, concurrent I/Os to the same logical volume.

EMC offers its Double Checksum product that verifies the integrity of Oracle data before writing it to its Symmetrix storage array and provides automatic notification of corrupt data. It also offers its Database Tuner product that identifies and models solutions to performance problems for Oracle and IBM DB2 UDB databases in Symmetrix environments.

These software extras should be considered if your environment wants to buy storage and is looking to address other issues in the enterprise as well. In cases where two or more vendors come in at about the same price point and measure up about the same in other desired areas, negotiating for features like these as part of the total storage package can help you both meet your immediate storage needs while economically solving some other internal business problems as well.

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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