Adding network hard disk storage -- painlessly Here's how one company solved its capacity limitations with a dedicated network filer By Ron Levine

March  1998

Are huge files threatening your network's performance and capacity? Looking for storage options that are faster than optical jukeboxes, CD towers, or tape libraries? A hard disk filer could be the answer to your network capacity, performance, and file sharing problems. We detail how one company implemented its solution. (2,100 words, including one sidebar)

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torage seems to be everybody's dilemma. In the house, we never seem to have enough closet space as we collect more and more things. In that two-car garage, the "stuff" usually takes over, and the cars end up parked on the street. At the office, we always seem to be adding more filing cabinets, bookcases, and shelves.

It's no different in the network world. Everybody seems to be looking for ways to painlessly add more electronic filing cabinets (i.e., storage space). Yes, storage capacity is a big problem. However, today's new hard disk storage options make it possible to add high-speed, reliable storage onto Sun-based networks without sacrificing file access speed or system functionality. As network data collection and operations continue to grow, storage vendors are providing technology to meet these increasing needs.

Sun magnetism
SunWorld, in taking a look at available storage options, found that a new methodology for installing additional magnetic hard disk space across the network provided a high-performance alternative to adding lower performance optical disk, CD media, and tape.

Magnetic hard disk continues to be the storage performance leader. Its file access speed and data throughput capabilities cannot be matched by other storage devices. By integrating a dedicated hard disk filer into the network, a LAN can keep more files online, ready for immediate access without any degradation of system efficiency. And these files are accessible at speeds equal to or faster than local hard disk storage.

In an interview with Direct Connect Systems, a southeastern VAR specializing in network storage solutions, SunWorld learned that Sun Microsystems users could solve their network's hard disk capacity limitations easily with the addition of a dedicated network filer.

According to Don Schrenk, a storage consultant at Direct Connect Systems's Atlanta, GA, headquarters, many engineering firms rely on fast, immediate, online access to large numbers of huge files across their networks for day-to-day operations. These users must have access to network storage at local disk speed, or productivity could suffer.

The challenge
Engineering companies commonly use CAD (computer-aided design) software to reduce the time it takes to bring a new product to market by letting the engineer try out several different ideas and styles -- all on the screen. The computer software evaluates the product's design and makes adjustments as necessary; these design changes would have taken many tries to perfect if the product had to be physically built each time.

Enabling all of the CAD software's immense capabilities requires files that take up huge chunks of disk space. Developing a complex product involves many large files to depict every view of a design in the minute detail of the final product. The MIS manager in an engineering firm's CAD department is always on the lookout for new and innovative ways to keep files readily accessible, yet refrain from slowing down the system's throughput.

One such manager is Scott Cechovic, a network architect at ADTRAN, Inc. ADTRAN, headquartered in Huntsville, AL, with sales offices across the U.S. and a worldwide distribution network, is a designer, developer, and manufacturer of ADvanced TRANsmission products.

Since opening its doors with the breakup of the AT&T monopoly in 1986, the company has installed over one million ADTRAN-based local loops operating worldwide, making it a leading supplier of high-speed digital communications products. ADTRAN's digital data service (DDS), integrated services digital network (ISDN), and T1/high bit-rate digital subscriber line (HDSL) digital loop products are sold to the regional Bell operating companies, more than 1,300 independent telephone companies, corporate end-users, and OEMs.

The problem
ADTRAN's tremendous growth was straining its IS resources. The huge files required by the CAD software were negatively impacting overall network performance and threatening to fill its network's capacity. And these files could not be shared across the engineering development team, using Unix at their workstations, and the company's Windows NT-based PC users.

"What I wanted was a common pool of hard disk storage that would better serve our users across the enterprise; the goal was to keep more files available online and to implement full file sharing across the company, while at the same time improving the LAN's performance. The added storage had to be extremely fast -- equivalent to local hard disk storage speed even though it was coming across the network. It also had to be extremely reliable; a lost CAD file represents thousands of dollars in skilled employee time to reproduce," Cechovic explains.

As the network architect, Cechovic must be aware of what is current in the computer industry. "After researching the alternatives, I knew that expanded magnetic hard disk storage integrated into our LAN was what we needed. Other storage devices, like optical jukeboxes, CD towers, or tape libraries, would be too slow and would adversely affect both LAN performance and user productivity. A hard disk filer solution was the answer to our storage capacity, network performance issues, and file sharing problems."

The solution
ADTRAN turned to Direct Connect Systems, a storage consulting company it had used before. Direct Connect suggested a Network Appliance (NetApp) filer as the hands down choice to fulfill ADTRAN's requirements. (See sidebar, "Tech talk," for details on ADTRAN's LAN and the NetApp filer.)

According to Schrenk, this "box" provides the benefits of file sharing, reliability, high-speed performance, and ease of administration the company needs.

The NetApp filer has a 99.997 percent proven reliability rating. The filer's performance is faster than a local drive. And, because of its multiprotocol support feature, Unix and NT users can share stored files without using any emulation software on the clients. ADTRAN evaluated the NetApp filer, Model F520, for 30 days. Not only did it live up to expectations, says Cechovic, but administration of the system proved extremely simple; there are about 37 commands that operate the filer. Reboot was also extremely fast, taking between 30 and 60 seconds -- "very impressive." Growing the file system was a simple procedure that required sliding an additional drive onto the drive shelf and executing the command Add RAID. Five seconds later the usable disk space had grown. As a result of the favorable evaluation, ADTRAN ordered a filer. ADTRAN's NetApp filer was equipped with 80 gigabytes (GB) of hard disk in a RAID Level 4 configuration. Since the initial installation, they've added another 80 GB of hard disk space. A nice feature of the NetApp filer is that adding additional drives or replacing a failed drive can be performed with little impact to users, Cechovic says.

After installing the NetApp filer, ADTRAN discovered another unexpected benefit: An innovative, versatile feature called Snapshots, which could be utilized by the company in a number of ways. With Snapshots, a system administrator can store up to twenty read-only versions of files. Snapshots allows users to recover deleted or modified files without requiring a restore from tape backup. To recover a lost or deleted file, the user copies the file from the Snapshots directory.

"We are also utilizing this feature to hold backup indices that track files written to tape. These indices (that range in size from several hundred megabytes to two gigabytes) point to and can track every real file put on tape. And, ADTRAN's 70 sales people have their e-mail safely protected by Snapshots. The company holds a "snapshot" of all POP3-based e-mail (and Exchange personal folders in the near future) for seven days so that, if needed, it can be recovered without going to tape backup. These two functions have become important secondary uses of the product and save ADTRAN system administrators a lot of headaches when it comes to file protection," Cechovic says.

The result
"The dedicated NetApp Filer's features, functions, and performance have all contributed to ADTRAN's successful servicing of its engineering CAD files with the least amount of administration and with a high degree of uptime," Schrenk says.

The primary use of the Network Appliance filer at ADTRAN today is in its Solaris environment. However, many more NT users are soon to be added. ADTRAN plans to upgrade to the next version of NetApp software (to be released in April) that has expanded support for NT users. "While high-speed additional network storage capacity and enterprisewide file sharing were the main reasons for installing the NetApp filer, we've found an important secondary use in the Snapshots feature," Cechovic says.

At this time, ADTRAN has about 40 users accessing the filer through the company's client/server Fast Ethernet LAN. These are mostly development engineers storing their large CAD files and backup file indices on the Network Appliance device. Its filer, which is available 24 hours a day and supports remote access, contains 160 GB of usable hard disk space -- Cechovic believes this will be enough for the office for the next year. After that time, he can upgrade the filer with additional or larger drives, if needed.

Resources

• Direct Connect Systems http://www.directconnect.com
• Network Appliance Filer Model F520 http://www.netapp.com/products/level3/index.html#NAF520

About the author
Ron Levine is a freelance writer based in Carpinteria, CA. He specializes in networking, storage device, and emerging technology applications. His most recent features for SunWorld were "Choosing the best type of high-end tape backup" (January 1998) and "Stretching the LAN," (August 1997). Reach Ron at ron.levine@sunworld.com.

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Tech talk

The NetApp F520 filer (an NFS file server appliance) is integrated into the LAN as an extension of the Sun servers' hard disk capacity. Because the filer employs no proprietary hardware (it employs standard Alpha or Intel hardware and an EISA bus), a simplified operating system designed just for file serving, a streamlined mother board, a RAID storage configuration, and device component redundancy, the NetApp filer's reliability approaches 100 percent uptime.

The filer's high performance is due to a number of storage technology advances, including:

• WAFL (write anywhere file layout) file system. Network Appliance pioneered this storage technology that reduces speed bottlenecks of the drives.

• A simplified operating system, called Data ONTAP, consists of only 300,000 lines of code. This is extremely efficient compared to using a traditional Unix or NT operating system, which is about 7 million lines of code and 10 million lines of code, respectively.

• The use of NVRAM split into two banks. As write commands come across the network, they first go through a semantic check and then are journalized into the NVRAM. After 10 seconds or when one bank is filled, the filer does a full-striped write. This consolidation and journalizing of writes increases performance of the writes.

• Read ahead caching. Read performance is increased by full read ahead caching on files less than 100 K in size.

Other NetApp F520 filer features include:

• Support for multiple protocols natively within the operating system. Current protocols supported are NFS (Unix), CIFS (NT and Windows), and HTTP. This permits the sharing of files across the LAN. The filer can also support static Web files.

• The NetApp filer utilizes RAID (redundant array of inexpensive disks) to ensure data protection. Its storage configuration also ensures disk reliability and fault-tolerant data availability. Fault-tolerant storage is accomplished in the NetApp filer by utilizing a redundancy scheme that guarantees the continued operation of the disk array itself if any one of its component parts (e.g., disk drive, fan, power supplies) fails.

• The NetApp filer employs RAID Level 4 technology. RAID 4 stripes data across all system drives, reserving one as a parity-bit drive. With RAID 4, if any one drive fails, data from that drive is recreated from the information stripes recorded on the other drives or rebuilt from the parity drive. RAID 4 is used in network applications where large blocks of data transfers are the norm.

• The NetApp filer fault-tolerant protection permits the removing or adding of an individual drive without interrupting network access to the storage subsystem. The filer also has the ability to automatically activate a built-in spare drive if a fault occurs on a working drive. The RAID subsystem rebuilds the data from the failing drive onto the spare drive without user intervention.

• The Network Appliance filer plugs into an available 10BaseT, 100BaseT, FDDI, ATM, Gigabit Ethernet, or multiple combinations of each port on your LAN. It takes only a few minutes for the filer's embedded software to detect and configure itself to your existing Solaris configuration and begin running as a dedicated file server.

• The Network Appliance filer measures 8.75"(H) X 17.25"(W) X 22.0"(D) and weighs approximately 53 pounds. It can hold a maximum of 28 drives; those drives being 4 GB, 9 GB, or a combination (your choice). The filer's maximum storage capacity is 232 GB. Prices begin at $20,000.