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Spotlight on midrange arrays

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By allowing overprovisioning of disk capacity, 3PAR provides an efficient way to dole out disk space.
3PAR InServ Storage Server
3PAR Inc., Fremont, CA, uses clustering in its InServ Storage Server to ensure availability, improve performance and provide scalability in its arrays. These arrays offer capacities that would dwarf the specs of most midrange systems. But 3PAR adds a twist to its clustering architecture by adding thin provisioning to control the allocation of capacity.

Two models of 3PAR's arrays are available: the S400 and S800. The S400 (prices start at $100,000) can be configured with a cluster of up to four controller nodes, while the S800 can support up to eight controllers. In both systems, the controllers are linked to each other and to disk modules by a full-mesh backplane. Each controller has a dedicated 1GB/sec connection, so adding more controllers scales up capacity and performance. As would be expected in a cluster arrangement, if one controller fails, another controller node takes over the failed controller's tasks.

Controllers connect to drive chassis modules.

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An InServ server can support a maximum 64-drive chassis with a total of 2,560 drives. Each InServ model offers broad capacity ranges, with both starting at a mere 600GB; top end for the S400 is 192TB, while the S800 can scale up to 364TB. The arrays can also be configured with substantial cache to improve performance--up to 40GB for the S400 (8GB for control and 32GB for data) and 80GB with the S800 (16GB control, 64GB data). InServ supports AIX, HP-UX, Linux, Windows, Novell NetWare and Sun Solaris.

The effectiveness of 3PAR's design has been confirmed with impressive performance numbers. On the Storage Performance Council's standard benchmark, the SPC-1 an eight-node configuration scored 100,000 IOPS.

But thin provisioning looms as the real star of 3PAR's highlight film, leveraging the InServ controller's ability to virtualize all of the managed storage into a common pool. With thin provisioning, you can allocate more storage than is physically present, so an application can be allocated as much storage as it's likely to need over the long term. But while the application may think it has a large amount of storage, actual storage is only pulled from the pool on an as-needed basis when the application writes to disk. This can help users to avoid overallocating physical resources and additional disk purchases can be delayed until they're needed. When additional disk is required, it can be added to the array non-disruptively, without having to take controllers or other storage offline.

Based on an easily upgradeable blade architecture, the Titan SiliconServer offers high-performance NAS file sharing.
BlueArc Titan SiliconServer
When storage vendors talk about modular storage, the "modularity" of the system refers mainly to the ability to plug in more capacity. Given a controller, you simply add more disk drives or disk shelves to get more capacity. If you start to max out the performance of a given controller, however, it's time to buy another modular array.

"To me, true modularity means being able to start in the basement apartment and go all the way up to the penthouse," says Arun Taneja, founder of Taneja Group, Hopkinton, MA. "I need to be able to grow in terms of capacity and performance."

San Jose, CA-based BlueArc Corp.'s storage platform scales not only in terms of capacity, but via throughput and connectivity as well. As a high-performance NAS array, a single Titan SiliconServer comes with a baseline 5Gb/sec of throughput, but can scale to 20Gb/sec. Capacity-wise, the Titan supports a single file system of up to 256TB across four tiers of disk drives. Those tiers include two classes of enterprise-class disk, the 15,000 rpm and 10,000 rpm Fibre Channel (FC) disk drives, and two classes of SATA drives, the 7,200 rpm and 5,400 rpm models.

Furthermore, because of Titan's innovative blade-based design, it's relatively future-proof. For example, Titan currently connects to hosts using Gigabit Ethernet (GbE) blades. But when 10GbE becomes the norm, Titan users can simply swap out GbE blades for the 10 gig models. "We're always a blade away," says Mike Gustafson, BlueArc president.

One BlueArc innovation that pre-dates Titan is the implementation of its file system in silicon on a field-programmable gate array (FPGA). Prior to Titan, the FPGA-based file system was what allowed BlueArc to claim superior performance to other NAS arrays on the market. Now those same FPGAs have been ported to two separate blades.

Simply put, the BlueArc system is for users who need high-performance file serving, such as in the life sciences arena or for Internet service providers.

Dot Hill's midrange entry is a high-performance array specially tuned for large image and audio files.
Dot Hill RIO Xtreme
Need speed, but don't want to pay a Ferrari price? RIO Xtreme is the first product to result from Dot Hill Systems Corp.'s acquisition of Chaparral Networks last year, and is perfect for organizations that have high sequential data streaming needs such as audio/video editing or seismic processing.

The first RIO Xtreme model was the dual-controller C4200, with eight 2Gb/sec FC ports. Starting with a single 12-drive chassis, the C4200 offers 1.75TB in a 3U package that can be expanded to 28TB with the maximum 16 drive shelves. In January, the dual-controller C4400 was introduced with 16 host ports and a choice of FC, SCSI or SATA disk drives.

The C4400 model is equipped with two 2U, 12-drive JBODs, and delivers the performance of 780MB/sec from disk and even more if from cache. In contrast, a comparable SANnet II, Dot Hill's more mainstream FC array, delivers 380MB/sec, or less than half the streaming throughput. Furthermore, the C4400 can also be purchased with a separate Emulex InSpeed switched bunch of disks (SBODs) loop switch. An 11U configuration consisting of the controllers, two SBOD switches and four disk drive shelves produces 1,300MB/sec performance from disk.

Performance is RIO Xtreme's strong suit, but at a reasonable price. The RIO Xtreme FC JBODs with 3.5TB costs $82,512; with 9.6TB of SATA disks the list price is $88,588. The key to keeping costs down is Dot Hill's "switchless SAN" strategy, where you simply attach hosts directly to the storage array rather than to a switch, thereby eliminating the need for a costly switch infrastructure.

Another way of paring costs--without impacting streaming performance--is using lower-priced disk drives. While previous RIO Xtreme versions used only FC or SCSI drives, the latest model supports SATA. Omar Barraza, Dot Hill's director of marketing, anticipates the SATA drive option will be popular with customers who have largely sequential data access needs, as opposed to more write-intensive IOPS operations.

The SATA drive option also plays well to customers with large capacity needs. Using 400GB disk drives, the RIO Xtreme's 192 drives deliver 78TB of raw capacity.

This was first published in March 2005

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