IP Storage Devices

In the past, an IT manager's only option might have been an expensive and complicated FC-SAN solution, because a less expensive NAS configuration couldn't provide the block-level storage needed for applications like Exchange Server and hefty database applications, such as SQL Server and Oracle. Today, a number of NAS manufacturers have adopted the iSCSI protocol, letting you create easily scalable iSCSI volumes within its shared file space.

This is an interesting development because the choice between block-level and file-level storage no longer determines your storage model--one networked device can manage file shares and block storage simultaneously. This amalgamation of iSCSI SAN and NAS is a true marriage of convenience, combining the ease of use of a NAS appliance, virtualized block-level storage, and a familiar and popular network fabric.

Such a device offers powerful storage-virtualization capabilities that let you create storage pools, introduce arrays and create volumes. You also can increase existing block and file storage dynamically without taking the system down, and without repartitioning and formatting existing volumes. This level of storage management was nonexistent or relegated to high-end SAN environments only a short time ago, but it's becoming more common with the newest generation of IP storage devices.

Below we examine three scenarios and three iSCSI-capable storage devices that represent three levels of affordable IT solutions: a NAS based on Windows Storage Server, a NAS running a Linux NAS OS, and a modular iSCSI SAN.Our first example is a company that has a small, growing workgroup with 100 Windows-only desktops and an Exchange server that's starting to run short on storage. Users store their data locally, backups are spotty at best, and there's little technical support readily available. Primary considerations before jumping to IP storage are cost and ease of management, followed by features and scalability.

For this scenario, we looked at Hewlett-Packard's ProLiant DL380 G4 Storage Server, a NAS appliance based on the Windows Storage Server OS. Originally marketed as a general-purpose 2U server, the DL380 G4 is available in both standalone and gateway models that can support external SCSI or SATA (Serial ATA) arrays. The base standalone unit we reviewed was priced to include both the optional ProLiant iSCSI Feature Pack software and four hot-swappable 146-GB Ultra 320/SCSI drives for 587 GB of internal storage.

The combination of the flexible DL380 G4 and WSS (Windows Storage Server) was a good fit with our low-cost and ease-of-management goals--a single device provides shared storage for the existing workgroup and offers additional block-level storage to extend the usefulness of the Exchange server already in place. WSS provides a comfortable entry point for Windows-oriented environments because of its familiar user interface and seamless compatibility with the Windows desktop. Plus it offers full support for Unix, Linux and Macintosh systems as needed.

HP's customized storage-management interface is well-designed and offers convenient access to most of the administration tools you'd need. With the handy Web-based control, you can manage the DL380 G4 from any location on your network and, if necessary, access the Windows desktop for low-level OS management and software installation. An optional expansion pack offers support for iSCSI, providing the software necessary to establish the DL380 G4 as an iSCSI storage target and support the creation of a virtual raw storage volume in the arrays file space.WSS's substantial storage capabilities are normally associated with more expensive products. The Virtual Disk service provides a standardized interface for expanded multivendor device support, and Multi-path IO lets you increase network connectivity and reliability through the use of multiple NICs or HBAs. WSS supports Microsoft's DFS (Distributed File System), which lets you publish virtual root and shared directories spanning multiple physical devices and locations. It also offers Shadow Copies of Shared Folders, which are snapshots of shared directories taken at specified times, letting users go back through a folder's history and restore accidentally deleted or overwritten files without IT's help or restoring from tape backup.

The DL380 G4 offers redundant power supplies, dual Gigabit Ethernet ports, redundant cooling and an external Ultra 320 SCSI port for tape backup. WSS is completely compatible with Active Directory and offers full support for most Windows third-party backup, security and antivirus applications. The DL380 G4 also supports HP's Integrated Lights-Out Management--a system offering advanced, centralized hardware monitoring and management.

The base DL380 G4 has six hot-swappable cages for Ultra 320 SCSI drives. Two cages come filled with 36-GB drives dedicated as mirrored arrays for the OS, and the remaining four can be filled depending on your storage needs and budget. With four 300-GB disks, you've got 1.2 TB of raw storage. If you need more, there are higher priced, multiprocessor external SCSI and SATA versions that offer up to 36 TB of storage when combined with additional arrays. A gateway SAN version supporting 46 TB of raw storage is also available.

In the next scenario, we have a remote branch-office workgroup of 250-plus mixed desktops with several servers supporting file shares, databases and a messaging system--all of which have a serious need for additional storage. Skilled IT help is on staff, but spread too thinly to deal with a system that has outgrown its resources. Primary considerations are cost and scalability, followed by ease of management and features.

A cost-effective choice for a slightly larger environment, the Snap Server 18000 by Snap Appliance (a division of Adaptec) is the pinnacle of Snap's NAS family. This powerful appliance combines affordable SATA storage with native support for iSCSI NAS volumes. The 18000 we tested was configured with eight hot-swappable 250-GB SATA drives for a total of 2 TB of raw storage.The 18000 runs on Snap's Linux Guardian OS 3.1, which emulates servers and supports clients on Unix, Linux, Macintosh OS 10.2 and Windows and includes Active Directory compatibility. Also, it lets you choose a Windows- or Linux-oriented security model during share creation. The browser-based Snap Server Manager configuration tool is intuitive, using Java applets for low-level management functions, such as creating arrays, and it can be managed from anywhere in your network.

The 18000 uses a "soft array controller" strategy for the disk system, which means that the management of physical devices, designation of arrays and allocation of raw volumes are handled by the OS rather than a hardware ASIC. Arrays of up to 24 SATA drives spanning multiple enclosures can be created as RAID 0, 1 or 5, and the system supports global hot spares for multiple-array configurations. The Instant Capacity Expansion feature of the Guardian OS lets you add and allocate physical storage to existing or new resources on the fly, reducing the need for downtime.

Surprisingly, even volumes designated for iSCSI can be increased dynamically without unloading and reloading data. This powerful tool remains invisible to the client devices and lets you seamlessly expand any type of existing volume in real-time, even across multiple physical arrays without interrupting processes on the client system.

The Snap Server 18000 has redundant power supplies and an onboard Ultra320 SCSI port, and is natively supported by most major enterprise backup applications. The 18000 also supports client or server drive imaging through the use of Symantec V2i Protector. Optional software supports asynchronous, server-to-server byte-level data replication over a WAN or LAN and offers data compression, encryption and bandwidth throttling using dual Gigabit Ethernet ports.A single Snap Server 18000 can be expanded to 30 TB of raw storage by connecting up to seven Snap Disk 30s--a 16-drive SATA expansion tray. Priced at $17,995, each Snap Disk 30 adds an additional 4 TB to the storage pool, enabling the system to grow with your needs. In an interesting twist, the devices interconnect using a dedicated FC link. Sure, you're thinking that this contradicts our goal of affordability, but aside from the FC cards and cables, it requires no additional FC hardware or storage experience to set up, as the link is invisible to the user.

In another transitional environment, a large company with hundreds of multiplatform users, multiple application servers and file servers is in serious need of storage consolidation. Management has been balking at the cost of buying into a monolithic FC-SAN package, but it can't ignore the amount of storage being wasted in multiple DAS locations, not to mention the time lost administering so many servers. Skilled IT help is available but struggling within a very constrained budget. Primary considerations are scalability and cost, followed by features and ease of management.

Question: When is $41,800 considered affordable? Answer: When the alternative is three to five times more expensive. At some point in the growth cycle, a move to a SAN begins to make a lot of sense, but not every budget can justify a six-figure SAN in addition to the required FC infrastructure. In this environment, the EqualLogic PS100E could serve as the cornerstone of a modular iSCSI SAN, offering enterprise-level features and storage at a fraction of the cost of an FC-SAN. The PS100E array we tested came with 14 250-GB hot-swappable SATA drives, offering 3.5 TB of raw storage.

SAN storage management is different than NAS devices management. The PS100E is a block-only device, and because there's neither an underlying OS nor the need to configure shares, you use the device's console over a serial connection to establish initial IP addresses and names, and choose RAID 10 or 50 storage schemes for the system's internal drives.

Once the initial addresses are configured, the system can be managed using a convenient Web interface that lets you create volumes, configure snapshot policies and include additional storage arrays as members of a virtual storage group. You can add more arrays as needed, dynamically increase the storage group's total space and the size of existing volumes, or create new ones without the need to take down the entire group.Setting up the system and mounting a volume on our test server was incredibly simple, taking less than 30 minutes, but remember that SAN storage provides only block-level storage and will require additional servers to support common shared storage or individual "home" directories for desktop users. Overall management is a little more complex than a smaller NAS configuration. On the other hand, block-level volumes are OS-agnostic--a SAN volume mounted on a server will act exactly like existing attached storage and can be used to replace or beef up existing DAS at server level, using familiar OS security and management tools.

The PS100E offers an impressive amount of enterprise-level hardware redundancy, with hot-swappable cooling and power as well as dual replaceable communication modules offering a total of six Gigabit Ethernet ports and four serial connections. Each unit offers internal automatic load balancing and drive optimization, volume cloning and point-in-time snapshots, and is supported by most OSs, including Apple Macintosh OS, Hewlett-Packard HP-UX, IBM AIX, Microsoft Windows, Linux, Novell NetWare, Sun Solaris and Unix.

Although every EqualLogic PS Array can operate as a standalone unit, the firmware can provide single-point management for up to 32 arrays, making a whopping 100 TB of raw storage. The powerful embedded virtualization software enables load balancing and optimization features to transfer across multiple arrays, and each storage group can support up to 1,024 volumes across 256 hosts. With the addition of arrays, storage bandwidth and performance grows because each new PS100E linearly increases storage pool performance while adding to the number of Gigabit Ethernet ports.

The Final Roundup

From a performance standpoint, IP storage networks run at about half the speed of comparable FC installations, most of which are now a 2-Gbps standard. This will undoubtedly change with the continued growth of 10 Gigabit Ethernet, but the common availability and affordable pricing of 10 Gigabit Ethernet components may still be a year or two away. There are also some translation-based performance trade-offs on iSCSI volumes that are based on conventional file space, so a combined NAS-iSCSI SAN configuration may not be a perfect fit for extremely large databases or other high-performance applications.Another performance consideration lies in the fact that the HP and Snap single-headed NAS products we're proposing both route all traffic through two onboard Ethernet ports. As these systems grow using storage-only expansion modules, processing power and port count do not, creating the potential for performance dips during periods of extremely high usage. This is not an issue in the EqualLogic scenario, because each new array increases both available processing and bandwidth--but in all fairness, this solution is also dependent on other servers to provide network shares. That being said, we have to remember that affordability is our primary goal, and each product provides a cost-effective performance increase in its given scenario.

Each configuration is scalable and easy to manage, providing the convenience of a switched consolidated storage environment that offers both block- and file-level storage. Each lets you begin consolidating storage with the purchase of a single device and expand through cost-effective modular components when your servers get tight on space. Most important, IP storage can be bought for a fraction of the cost of FC and will run on any existing Ethernet infrastructure, regardless of speed.

Steven Hill owns and operates ToneCurve Technology, a digital imaging consulting company. Write to him at [email protected].

Let's face it--one company's idea of affordable might be completely out of reach for another. In this month's Affordable IT installment, we explore NAS and SAN storage devices and examine their capabilities for the smaller user base, a midsize organization experiencing growing pains and an enterprise with a watchful eye on expenditures.