Product Review: Entry-level SAN arrays square off

The days of adding a local disk to every server are waning. With the rise of the storage SAN, it's no longer necessary to make an educated guess on future storage needs when you spec server hardware. In a SAN environment, servers deliver data requested by the client applications; the SAN takes care of storing that data.

Even with the budget of a subterabyte network, the rewards of a SAN -- management, security, scalability, and performance -- are becoming achievable. Still, the leap from SAS/NAS to SAN takes a considerable investment, both in mind and budget. Dell Computer and Hewlett-Packard are hoping to smooth this ride by offering lower-cost, scalable arrays to meet the needs of the smaller IT shop.

The Dell/EMC CX200 array is the fraternal twin of EMC's CX200 -- a 2GB FC (Fibre Channel), 15-drive, fully redundant 3U rack-mounted array. HP's entry is the MSA1000, a 14-drive 4U rack-mounted array (4U with supplemental power supply), fully redundant, but also offering the benefit of 6- or 8-port integrated 2GB Fibre Channel switches. Both arrays list for less than US$35,000 fully loaded but provide the same benefits of their larger comrades. For pure performance and manageability, the CX200 edges out the MSA1000, but the MSA1000 leads in flexibility and scalability.

Where's my data?

Both Dell and HP have come a long way since the SAN dark ages of 2000, and Dell in particular is aiming at the entry-level market with the CX200. Dell has borrowed heavily from EMC to bring the CX200 to market; Dell is the hardware manufacturer of the CX200, not EMC, and provides end-to-end support on the array.

This partnership with EMC brings decades of storage experience to Dell's customers, giving Dell a running start into the storage market. Dell utilizes EMC software, including VisualSAN and Navisphere, to manage the CX200 and its larger siblings. Navisphere, the Java-based management console for the CX200 array controllers, is accessible from any browser with JRE 1.4.1. The interface, however, is decidedly not a standard Java interface. If the applet wasn't running in a browser window, it would be indistinguishable from a Microsoft Management Console plug-in, with hierarchical views of all displayed data, intuitive menus, and event flagging throughout the tree.

The application allows all forms of array management, from LUN (logical unit number) creation to storage groups management, as well as viewing the current state of every piece of hardware in the array. Navisphere's GUI was developed after the Navisphere CLI (command line interface) was written, every GUI action has a CLI equivalent -- a definite plus.

While the CX200 can be fully configured from Navisphere alone, Dell wrapped these tools in a much broader SAN management package called VisualSAN, with Dell-specific components to integrate with Dell OpenManage server tools. VisualSAN takes SAN management to a whole new level, providing a real-time graphical view of the SAN, with color codes determining link type, server presence, and overall SAN health.

VisualSAN plug-ins add more features, including Performance Manager, which gathers real-time statistics and creates charts of SAN performance, permitting simple trend analysis and troubleshooting. Configuration Manager includes features such as configuration snapshotting, which allows the administrator to create a data file containing every relevant data point in the SAN infrastructure. When a problem later occurs, it's simple to compare a known good configuration to the current state to pinpoint the problem.

VisualSAN isn't necessarily cheap at US$4,000, and Performance Manager and Configuration Manager are an additional US$5,000 each. While this may be a large percentage of the cost of a small SAN, the ability to implement these packages as the SAN grows is valuable.

The CX200 has some limitations, such as the lack of file system snapshotting and array mirroring. These features are only present on the higher-end CX series arrays. Also, the CX200 only supports 15 connected servers, with each member of a cluster counted separately. The CX200 is limited to 30 drives, and scaling beyond this limit requires an upgrade to CX400 storage processors.

The MSA1000, on the other hand, can scale to 42 drives, for a total of 6TB of storage (the CX200 tops out at 4.4TB). Dell does offer an ATA shelf for the CX200, which bumps the maximum storage to over 8TB but with a mix of SCSI and IDE disk.

HP's MSA1000 is in the same space as the CX200 and was designed specifically for the first-time SAN buyer. While it's possible to upgrade a CX200 to a CX600 and see a performance boost, the MSA1000 isn't quite as expandable because it doesn't integrate with HP's EVA line, although it exists on the same fabric.

Like the CX200, the MSA1000 is more at home in a homogeneous environment of same-brand servers. HP has strict guidelines on the compatibility of server models, FC (Fibre Channel) HBA (Host Bus Adapter) controller models, server operating systems, and the MSA1000. While HP's FCA2214 HBAs work nicely under RedHat Linux Advanced Server 2.1, the same HBA will not communicate with the MSA1000 under Windows 2000/2003.

One of the MSA1000's definite advantages is the optional integrated FC switches. Rather than purchasing separate FC switches to build the SAN fabric, you can implement the integrated redundant 8-port 2Gb FC switches directly into the MSA1000 chassis, saving significant cost and implementation time. HP also offers an integrated 3-port FC-AL hub for the MSA1000 that is aimed at small clusters. These switches and hubs are managed via a built-in Web interface, and offer most of the features found in outboard FC switches, such as port and WWN (World Wide Name) level zoning.

SANity Test

The CX200 edged out the MSA1000 in all performance tests, but the MSA1000 was no slowpoke. On average, the CX200 held a 5 percent edge over the MSA1000 in I/O per second and total throughput. Both arrays performed without a hitch when controllers, power supplies, and FC links were abruptly removed. Dell's PowerPath software handles the host side of FC link redundancy and doesn't yet support Windows 2003, but it will be supported in early July, according to Dell. HP's equivalent -- SecurePath -- currently supports every OS that the MSA1000 supports.

The major difference between the MSA1000 and the Dell CX200 is management. Dell offers a wide range of configuration and monitoring tools for the CX line, a significant benefit over HP's MSA1000. Management of the MSA1000 is done through HP's Array Configuration Utility. This utility can be run from a bootable CD or from a Linux or Windows server attached to the array, but it is not otherwise accessible. CIM (Compaq Insight Manager) the overall HP server-monitoring package, does handle monitoring of the MSA1000 array and is a very valuable tool for server monitoring, but the available MSA1000 monitoring tools still take a seat behind the CX200's options.

But what the MSA1000 lacks in management tools, it makes up for in available integrated components and scalability. The MSA1000 will address more total storage than the CX200 and can handle more hosts. One impressive feature is the ability to move an existing RAID diskset from a ProLiant server to the MSA1000 without losing the data stored on the logical volume. This is because the MSA1000 utilizes HP's tried-and-true SmartArray RAID controllers to drive the disks. Also, unlike the CX200, the MSA1000 has no restrictions on disk placement; it's possible to move drives around within the shelf, and the arrays will remain intact.

Furthermore, the MSA1000 has an edge in reliability; all array configuration data is stored on each disk. The CX200 stores this data across the first five drives, which must remain in their original position to assure normal function.

Overall, the best bet for any infrastructure is to maintain homogeneity. If most servers are made by Dell, then the benefits of VisualSAN and Dell OpenManage integration will make configuration and administration easier. If the servers are Compaq or HP ProLiant systems, then the MSA1000 is a better fit. For those in between, the decision shouldn't be made without specifically checking HBA and array compatibility - but rest assured that either solution will perform well.

For pure performance and manageability the CX200 edges out the MSA1000, but the MSA1000 leads in flexibility and scalability. Either way, mature storage consolidation in the small datacenter is here.

All the arrays tested had a total capacity of approximately 1TB, using 73GB drives, and were limited to a single shelf. The lab configuration for all arrays was a 2Gb SAN fabric, switched by McData Sphereon FC switches for the CX200, and the integrated 8-port FC switches for the MSA1000. The reference servers used were a Dell 2650 with dual 2.4GHz Hyper-Threaded P4 Xeon CPUs and 2GB of RAM, and an HP ML370 with dual 2.8GHz Hyper-Threaded P4 Xeon CPUs and 1GB of RAM.

The arrays were run through a battery of tests across several operating systems -- Windows Advanced Server 2000 SP3, Windows Enterprise Server 2003, Windows Standard Server 2003, and Red Hat Linux Advanced Server 2.1. Performance testing on the Windows platforms was done with SiSoft's Sandra 2003 and Bonnie++ on the Linux platforms. Additionally, array degradation and rebuild test data was gathered with Bonnie++ on Red Hat Linux AS 2.1, measuring array performance under adverse conditions with the controllers configured to allow high-priority array rebuilds. All tests were performed on a five-spindle RAID5 array with a single 200GB logical drive, formatted with NTFS for the Windows tests and ext3 for the Linux tests.

All Web-based configuration testing was attempted with a variety of browsers across several platforms, including Linux, Windows, and Mac OS X.

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