Network Attached Storage Treads New Turf
Network Attached Storage Treads New Turf
By Elizabeth Clark , Network Magazine
Jul 7, 2002 (6:49 AM)
URL: networkmagazine.com
Seismic shifts have rocked the Network Attached Storage (NAS) market over the past year or so. The imaginary fault line that once divided NAS and Storage Area Networks (SANs) is disappearing as the chasm between the two technologies narrows. It's become clear that there's room in enterprises, data centers, and service provider networks for both NAS and SANs, and that both can thrive in the same environment.
One of the most dramatic movements has been the rise in the popularity of NAS devices. According to a recent report by the Yankee Group (www.yankeegroup.com), revenue for the NAS storage systems market in 2002 will grow 12.6 percent over last year's figures. By 2005, NAS system revenues will reach $8.56 billion.
Changes have also occurred in the types of devices in the NAS category. Here's a look at the landscape: "Traditional" NAS is linked directly to a network and provides file-level (as opposed to Fibre Channel's block-level) access to data. NAS aims to separate the storage from the system-in other words, to enable data storage on devices that can be accessed via a network, as opposed to a separate disk system.
NAS systems can accommodate various protocols, including HTTP and FTP, Network File System (NFS), and Common Internet File System (CIFS). Different NAS systems also support different OSs and platforms (Windows, Unix, Linux, Solaris, NetWare, and AppleTalk are among the most common), but clients running on different OSs can typically share files. Some systems have their own proprietary OS.
NAS devices generally include Gigabit Ethernet interfaces. Some NAS systems come with their own backup and management software, and many are compatible with storage-management software from vendors such as Veritas (www.veritas.com), Legato (www.legato.com), NSI Software (www.nsisoftware.com), and Computer Associates (www.cai.com).
Initially, a NAS device was an unsophisticated dedicated file server. While many of the more basic systems are still on the market, some vendors also offer NAS gateways, also called "NAS heads." These appliances contain no internal storage, but instead connect to storage devices via direct attachment or through a SAN. NAS gateways are connected to back-end SAN-attached storage systems, helping bridge the gap between the two technologies.
NAS is usually less pricey than SAN technology, but is also less efficient at certain operations. At present, some applications are simply better suited for Fibre Channel SANs. In addition, SAN proponents argue that NAS is less stringent in its security capabilities. After all, NAS is based on IP, as opposed to the traditionally more trustworthy Fibre Channel that SANs use.
These distinctions in performance and security are likely to blur as NAS devices deliver more horsepower, and as Ethernet and IP networks and SANs converge. Many industry observers believe SAN and NAS convergence is inevitable, and some products we'll discuss later will support that premise. However, it isn't clear exactly what the term convergence means, how quickly it will occur, and what its long-term implications will be. In this article, "convergence" refers to technologies that facilitate the sharing of block- and file-based data, and that join IP-based NAS with Fibre Channel-based SANs and with IP-based SAN systems.
Many NAS systems include built-in security features, such as file locking, authentication, encryption, and error detection and notification. They also include access control via mechanisms, such as Access Control Lists (ACLs), and options for setting up permissions. Support for Secure Sockets Layer (SSL), as well as Lightweight Directory Access Protocol (LDAP), Remote Authentication Dial-In User Service (RADIUS), and Kerberos authentication are common.
Firewall protection is helpful, but not foolproof. Some NAS systems have the primary security functionality built into their products' software, or they rely on security mechanisms in the OS. Third-party vendors such as Check Point, McAfee, Trend Micro, Symantec, and Secure Computing can also provide security.
NAS STRATIFICATION
Although it's becoming more difficult to segment the NAS market, entry-level to mid-range systems can scale up to 500 Gbytes for departmental and workgroup systems, and up to multiple terabytes for high-end enterprise-level systems. Some vendors have offerings in all segments of the market, but vendors such as EMC (www.emc.com), Network Appliance (www.netapp.com), and Storage Computer (www.storage.com) have dominated the high-end space. Sony (www.storagebysony.com), Maxtor (www.maxtor.com), and Quantum (www.quantum.com) have dominated the workgroup space. The overlap typically occurs in the mid-range space, with vendors such as Network Appliance, EMC, Compaq Computers (now part of Hewlett-Packard), IBM, Dell Computer, Procom (www.procom.com), and Quantum.
Although this article focuses on enterprise-level systems, it's important to provide some context. Products in the workgroup-to-midrange level include Quantum's Snap Server, Dell's PowerVault, Sony's StorStation, Maxtor's MaxAttach, and Compaq's NAS S1000.
One indicator of stratification is the price tag. For example, Quantum's workgroup Snap Server 1100 with 40Gbytes of storage costs $549, and Procom's NetFORCE 1750 with 1.8Tbytes of capacity costs $21,850. IBM's NAS 200 rack system with 109Gbytes of storage costs $23,852, and EMC's Clariion IP4700 starts at $75,000 for 400Gbytes of capacity. At the high end, EMC's Celerra File Server starts at $250,000 for 500Gbytes of capacity, but can scale into the millions of dollars. The figure shows projected worldwide NAS revenues through 2005, according to price range.
FASTER, SMARTER, CHEAPER
Many factors have contributed to NAS systems' enhanced performance and scalability. One of these is the emergence of TCP/IP offload engines, such as Host Bus Adapters (HBAs), or NICs, designed to handle TCP/IP processing, and free up server CPU for other tasks. In addition, NAS has improved performance in handling demanding applications, such as databases, which used to be NAS's no-man's-land.
Enter the Direct Access File System (DAFS), which promises to significantly streamline database operations (see "How Fast Can DAFS Make NAS?" June 2002). Developed by the DAFS Collaborative and spearheaded by Network Appliance and Intel, DAFS is a file access protocol designed to reduce the latency and increase the throughput of NAS systems. DAFS' direct memory-to-memory architecture helps reduce CPU overhead and makes it more efficient than the nearly geriatric NFS and CIFS protocols.
DAFS uses the Virtual Interface (VI), which is optimized for server clustering, boosting file sharing performance. DAFS is compatible with Fibre Channel, Gigabit Ethernet, and InfiniBand (see "Storage Networking: Fibre Channel, IP, and Beyond," June 2002).
Network Appliance recently introduced a DAFS-based product, the DAFS Database Accelerator. It's optimized for Solaris-based servers running Oracle8i and 9i, DB2, and Sybase. The software uses VI technology over Gigabit Ethernet, and has load balancing, multipathing (support for two or more data paths), and failover capabilities. In addition to backup and mirroring, it can perform database testing and online recovery.
According to Randy Kerns, senior partner with storage analysis firm The Evaluator Group (www.evaluatorgroup.com), DAFS is one of the most important recent developments in the NAS market. "Its appearance is dramatic," says Kerns.
W. Curtis Preston, president of the Storage Group (www.thestoragegroup.com), says DAFS' direct-memory access will provide a significant performance boost. Also, he notes, "You're going to have a protocol that was designed in the 21st century, instead of 1984, which is when NFS and CIFS were invented."
It's no secret that some backup and restore operations have been difficult with NAS, but this situation is also looking up. For example, Network Data Management Protocol (NDMP) specifies a protocol that storage management applications can leverage to perform backups of data on a network with various hardware platforms and OSs. This technology also facilitates LAN-free and serverless backup, which can dramatically improve efficiency.
Progress has also been made on pricing. Intense competition in the market, in addition to products such as Network Appliance's NearStore R100 and HP's StorageWorks NAS B3000, has made NAS more affordable. The R100 NAS appliance is a near-line storage system designed for backup and archiving. It ranges from 12Tbytes to 96Tbytes in capacity, and its software lets users make backups that can later be saved to tape. You can use the R100 to back up multiple file servers, and it's compatible with storage management software from vendors such as Computer Associates, Legato, and Veritas.
A 12Tbyte configuration (with mirroring, replication, and restore software) starts at $275,000. This brings the cost of disk-based backup and archiving closer to that of enterprise-level tape systems, but at much higher speeds than tape. ADIC (www.adic.com) recently announced that its tape libraries are compatible with the R1000. StorageTek (www.storagetek.com) and Quantum also say their tape-library systems are interoperable with Network Appliance's NetApp filers.
Another highly functional, yet reasonably priced system, is HP's NAS B3000, a mid-range NAS system with a capacity of up to 27Tbytes, with embedded switches. The system was originally a Compaq device, and due to the HP-Compaq merger, it might be integrated into another product line in the future.
The B3000 has backup and restore, replication, point-in-time copy (snapshot capabilities), and clustering capabilities. The system also provides virtualization, which enables you to make multiple physical devices on a network appear as a single image, and it allows a virtual "pool" of storage to be allocated more efficiently. Via a Fibre Channel link, the B3000 can connect to a SAN, providing both file- and block-level access. Pricing starts at $43,000 for 288Gbytes of storage.
The introduction of tools such as Microsoft's Server Appliance Kit (SAK) has also impacted the NAS market. This software enables OEMs to get NAS appliances to market faster and makes these devices easier for the network administrator to manage. Sun Microsystems recently released ServPoint Appliance Software for NAS, which is targeted toward resellers and system integrators. The software enables them to convert nonproprietary servers into Solarisor Linux-based NAS appliances. The enterprise then benefits from a wider range of choices.
THE EMERGENCE OF CONVERGENCE
The convergence of NAS and SAN technologies (in other words, block-based and file-based access) is beginning to reshape the NAS market. More vendors are rolling out NAS gateways and other devices that help to bridge the gap between NAS and SANs. Most of these products, combined with compatible hardware and software, provide features such as backup/recovery, replication, remote mirroring, snapshot capabilities, failover, clustering, remote management, and virtualization.
Products that deliver some form of convergence include EMC's Celerra File Server, which front-ends the company's Symmetrix storage arrays. The Data Mover 510 is a gateway that acts as a cluster of up to 14 dedicated file servers within Celerra and allows the Celerra to scale up to 52Tbytes of attached storage.
EMC's Celerra HighRoad software bridges NAS and SANs by providing multipath file sharing and delivery over SAN-based connections. It also supports local file system replication. EMC says it will integrate the Internet Small Computer Systems Interface (iSCSI) into future versions of its NAS systems, which would represent another step forward in convergence. But the company will likely take its traditional "wait and see" approach to technology shifts of this gravity.
IBM's TotalStorage NAS 300G is a gateway device that processes both block- and file-level data and links Ethernet LANs with Fibre Channel SANs. The system is compatible with IBM's Enterprise Storage Server, Module Storage Server, and FAStT200 and FAStT500 storage servers. IBM is linking the 300G with other vendors' SAN-based equipment.
For example, IBM has performed interoperability testing with Hitachi's (www.hds.com) Freedom Storage Lightning 9900 arrays, which include Fibre Channel SAN support. The single-node (G01) and dual-node (G26) versions of the 300G are $31,915 and $66,330, respectively. In 2001, IBM integrated iSCSI into its TotalStorage IP Storage 200i, a disk array that enables block-level I/O requests to be sent over standard IP networks.
HP's StorageWorks NAS Executor E7000 is a NAS gateway linked to the company's disk arrays. When combined with the Fibre Channel-based StorageWorks Enterprise Virtual Array (a virtual RAID system), the E7000 enables multiple Virtual Arrays to be presented as one storage pool. It supports both SAN and NAS technologies. Pricing for the system starts at $48,000. Like other vendors in the market, HP and Network Appliance have indicated they'll incorporate iSCSI technology into future products, but time will tell how quickly this will happen.
Taking a slightly different angle on convergence, Auspex (www.auspex.com) says its NSc3000 network storage controller was designed to interoperate with other vendors' existing SAN storage subsystems. The NSc3000 provides file services to the SAN via a switch.
Finally, vendors such as Intel, IBM, Sun, and Dell have introduced blade servers that support diverse protocols such as Ethernet, Fibre Channel, iSCSI, and InfiniBand.
THE NEW VIRTUAL REALITY
A veritable tsunami of virtualization products for the NAS space has hit the market. The term "virtualization" has been over-used, but it basically refers to the process of making disparate, heterogeneous devices on a network appear as a single logical pool of storage, and then allocating storage to servers on an as-needed basis. Virtualization can help optimize disk space use, streamline management functions, and simplify operations such as remote mirroring, backup and restore, and disaster recovery. It can also enhance Return on Investment (ROI) through more efficient sharing of storage resources.
According to The Evaluator Group's Kerns, managing multiple NAS devices as a single device "should drive down the costs of administering them, which has been one of the real problems with NAS."
Organizations have implemented virtualization in both software and hardware. Network Appliance's MultiStore software consolidates Unix and Windows servers and domains into a single appliance. The system enables logical partitioning of a NetApp filer's network and storage resources, in effect allowing one filer to act as multiple virtual filers. Users, domains, and data can be migrated to another filer for load balancing or disaster recovery. The software's security mechanisms are designed to prevent resource discovery or data access across the system's virtual partitions.
FalconStor's (www.falconstor.com) IPStor software provides storage virtualization and aggregation and provisions storage to Windows, Linux, and Unix systems. In addition to backup, mirroring, replication, and snapshot capabilities, it supports file- and block-level traffic over IP networks and enables SAN and NAS functionality. And Procom's DUET software, enables file- and block-level access for its NetFORCE NAS filers, which, at the high end, can support up to 17Tbytes.
Tricord's (www.tricord.com) Lunar Flare NAS appliances are aggregated into clusters by their Illuminata software. The software can cluster up to 16 systems into a single storage pool to serve Windows and AppleTalk clients. Based on a distributed file system, Illuminata reallocates data across multiple devices and manages the data and hardware as a single entity.
LeftHand Networks' (www.lefthandnetworks.com) Network Storage Module 100 operates via a technology the company calls "Network Unified Storage." The system runs over Ethernet and supports block and file transfers. It provides clustering and virtualization capabilities, as well as dynamic allocation of storage resources. The system includes Windows NT/2000, Solaris, and Linux support.
Pirus Networks' (www.pirus.com) PSX-1000 Storage Utility Switch is a router that enables heterogeneous resource consolidation, centralized management, and on-demand provisioning. The system manages both block- and file-based storage and provides virtualization capabilities.
Other vendors whose products support virtualization (or virtualization-type functionality) include IBM Tivoli (www.tivoli.com), EMC, HP, Veritas, and DataCore (www.datacore.com). Sistina Software (www.sistina.com), Zambeel (www.zambeel.com), and Cereva Networks (www.cereva.com) are among the more recent players.
NEXT-GENERATION NAS
New developments are extending NAS's reach, speed, and functionality into a new dimension. Loosely referred to as next-generation NAS, or utility-class storage, it includes faster, and more intelligent, scalable, reliable, and fault-tolerant systems that can provide advanced QoS and provisioning features and enhanced management capabilities. Devices in this category can typically support many more connections than "traditional" NAS systems. Distributed storage-caching systems targeted toward storing the most frequently requested files at the network edge are also expanding the functionality of conventional content delivery to address storage-specific issues.
According to BlueArc (www.bluearc.com), its Si7500 Storage System can deliver 2Gbytes of throughput. The system has a capacity of up to 8.76Tbytes per cabinet and can scale to 250Tbytes when multiple cabinets are linked via a NAS gateway. The Si7500 has a NAS front-end interface and a Fibre Channel SAN back-end interface. The system uses high-performance processors and storage networking switches from Vixel (www.vixel.com) to facilitate its throughput level.
Storage Computer's CyberNAS 4000 extends NAS to the MAN and WAN. The system provides Gigabit Ethernet and OC-48 connectivity and up to 43.9Tbytes of storage. It has multiple high-speed interfaces that facilitate transmission of content such as video, graphics, and large databases. The system supports SCSI and Fibre Channel Arbitrated Loop (FC-AL). In addition to mirroring and replication, the CyberNAS 4000 enables the establishment of geographically dispersed clusters.
Systems from vendors such as Tricord, LeftHand Networks, Pirus Networks, Cereva Networks, 3PARdata (3pardata.com), and Zambeel could also be included in the utility storage category under the definition used here.
In the distributed storage arena, Network Appliance's content-delivery appliance supports over 155Mbits/sec for HTTP and more than 622Mbits/sec for streaming applications. The NetCache C6100 can store and access content libraries totaling up to 2Tbytes, and operates via customized content management and delivery software. Security features include filtering and virus scanning, LDAP and RADIUS authentication support, and ACLs.
Storigen's (www.storigen.com) Edge Linux-based Storage Server stores and delivers content such as files, as well as Web and streaming media traffic at the network edge. The system can store up to 2.5Tbytes of data and can deliver content at up to 500Mbits/sec. The server functions via the company's software, which provides remote monitoring, management, and distribution. Security mechanisms include filtering, as well as SSL and LDAP authentication support.
AS THE GROUND SETTLES?
Expect to see extensions of the current developments in the NAS market, as well as new twists. Convergence will continue, with the introduction of more systems capable of handling block- and file-level data. More NAS vendors will introduce systems compatible with protocols such as IP, iSCSI, and InfiniBand. NAS gateways will become more abundant.
Developments in virtualization, global distributed file system capabilities, and automation will also continue. Interest in Storage Resource Management (SRM) software, which performs functions like disk space quota monitoring, discovery, and root-cause analysis, will heat up.
But the road ahead won't be without potholes. While the industry will make some strides in interoperability, some vendors won't be so eager to "compromise" their proprietary platforms. The fact that so many of the standards that could affect the NAS market are either new and basically untested, or still awaiting finalization, could generate some tremors in this territory. In addition, iSCSI could actually become a competitor to NAS, depending on the adoption rate of the technology. And the NAS market is already jam-packed with far more vendors than it can support, so expect some dropouts along the way.
Elizabeth Clark, executive editor, can be reached at eclark@cmp.com.
Resources
Using SANs and NAS, by W. Curtis Preston (O'Reilly & Associates, 2002, ISBN: 0-596-00153-3) provides a comprehensive, practical guide to NAS technology. For more information, go to www.oreilly.com.
For a white paper from The Evaluator Group called, "An Overview of Network Attached Storage," go to www.evaluatorgroup.com.
A white paper from the Storage Networking Industry Association, "Shared Storage Model," describes many aspects of NAS, its functions, and its role in networked storage. You can find it at www.snia.org/English/Collaterals/Whitepapers/Shared_Storage_Model/pdf.
For news, white papers, and related information on NAS, go to www.enterprisestorageforum.com. |
