focus topic: AS/400 Storage Trends
Storing organizations’ ever-increasing business data directly on the AS/400 hard drive quickly uses up disk space, leads to reduced performance and can even cause the ever reliable AS/400 to fail. It is essential that data storage allow for easy retrieval and reliable restoration as well as provide for disaster recovery. Therefore, AS/400 users must develop a storage plan that incorporates the right combination of the three basic storage mediums for their business: direct access storage devices (DASD), optical and tape.
Every business needs to create a hierarchical storage management (HSM) plan to deal with data and allocate that data into immediate, short term and long term storage at specific time intervals. Since no two businesses are the same, no two HSM plans will be exactly alike. One company may require quick access to certain data for just a few days while another may need to keep similar data accessible for a month. Thus, IT managers and individual businesses must review company needs and requirements to develop the best HSM for their company.
Without a plan, confusion over what data to store on which media and when to move the data is inevitable. It helps to take a look at each storage media in light of features, benefits, and costs. DASD is like an external zip drive for a PC; it gives you greater storage capacity without having to replace the existing drive. DASD provides for fast data retrieval, can be configured as part of AS/400 and be installed and serviced by IBM personnel as part of the AS/400 service agreement. Optical storage provides for nearly indestructible data storage with excellent retrieval properties. Tape storage continues to be enhanced through changes as innocuous as altering the starting search point to the center of a tape to speed up the tape storage retrieval process.
As you go up the pyramid in Figure 1, costs go up but retrieval time is reduced. Memory has the fastest retrieval rate but its use is the most costly. Solid state disks provide the next fastest retrieval rate, but its cost is still significant. DASD provides for lower cost storage but retrieval lags behind memory and disks. Optical solutions lower the costs even more, but since the optical disks are stored separately, retrieval is slower. Tape library storage has the slowest retrieval rate, but the costs associated with tape are dramatically lower than any other storage media.
The kind of data being stored and retrieval requirements determine the type of media to use. Legal documents, for instance are typically stored on optical while daily transactions are stored on DASD.
DASD installations are a quick fix. When the system shows 90 percent capacity and performance is degrading, adding a DASD is a fast, easy solution. The DASD install increases capacity and maintains performance levels. However, with a constant influx of new data, this use of DASD only serves to postpone a storage decision, not make one.
This has not stopped DASD manufacturers from increasing the speeds and capacity of the devices nor have customers stopped buying them. A common use for DASD is mirroring to protect against system downtime. For example, The Popular Club Plan, a New Jersey-based retail mail order company, needed to be up 24 x 7 so its operators could enter and process orders. Popular Club’s Mike Kupchik comments, "Our system is mirrored. We are very negative about downtime and the only way to stay up if you have a failure is mirroring. However, this doubles the DASD, since when you write a transaction to one of the disks you simultaneously write it to the other."
DASD can be added either internally, which takes advantage of the power supply, secure connections, and includes the DASD in the AS/400’s service agreement; or externally which requires a separate power source and must be covered under a separate maintenance agreement. A common practice is to use the room inside the AS/400 to capacity and then add external DASD as needed. Decision Data’s e-RAID, for example, can be attached as either an internal DASD replacement or as an external DASD supplement.
To reduce the physical space needed to store documents, documents must be transferred to smaller, retrievable media. In the past, that media was microfiche or microfilm. The time and effort involved in retrieving documents from microfiche or microfilm is contrary to today’s need for instant response. Also the film has a tendency to degrade over time making this a less reliable document storage solution.
Optical storage provides for two features needed in a storage plan: retrievability and reliability. Optical disks stored in a juke box are the new document storage solution. They provide for easy document retrieval and can be printed to appear like an original. When stored correctly, optical disks do not degrade over time and are virtually indestructible. This makes them an excellent choice for storing documents.
When you can store all the documents from a file cabinet on one disk, the required storage space is reduced resulting in more productive use of real estate. Jeanne Wymer of W. A. Foote Memorial Hospital in Jackson, Michigan says, "With the high cost of real estate within hospitals, if you can get rid of the file rooms you can gain a lot of valuable space." Optical storage is the preferred medium for many document imaging programs. Wymer explains, "We use optical for our document imaging system. We are working toward electronic medical records; right now we have most of our outpatient records and ER records back to 1994, and we do COLD (Computer Output to Laser Disk) storage of payment vouchers, bills and UB92s for our business office. We store these on optical platters and use the IBM 3995 LAN attached juke boxes so that we can attach them to both of the AS/400s. If we are in a role swap situation, we can still access our optical platters from our backup system."
She adds, "Another advantage of storing records to optical rather than tape is the retrieval time. There is no operator intervention required to retrieve the documents off optical. The only thing users notice, if it is on optical rather than DASD, is that it takes a little bit longer."
Advancements in tape technology are making tape more viable as both a long and short term storage media. For example, Irvine, CA-based tape solutions vendor BCC Technologies has announced transfer rate improvements in excess of 50 GB per hour using dual tape drives. David Breisacher, CEO/Chairman of BCC Technologies, Inc. says, "BCC’s new tape libraries have been specifically designed to compete with IBM’s Magstar 3570 and 3590. After listening to numerous AS/400 customers complain about Magstar’s high price, disappointing backup rates, and small cartridge capacities we decided to develop a tape library that would address these issues."
IBM has developed Magstar 3570 MP as a multi-purpose solution. IBM’s Senior Technical Staff Member, John Gniewic says, "3570 is a balance between capacity and data rate, but also has the features of fast access time and permanence. 3570 is beginning to get characteristics that make it applicable for some of the same kinds of applications as optics. 3570 MP is optimized for a combination of functions including some of the on-line applications that are traditionally done by optical."
Since switching to IBM Magstar 3590 tape drive from a competitor’s product that had several disk jamming problems and read/write errors, Popular Club’s Mike Kupchik can’t be happier. He says, "We just purchased three 3590’s, which are extremely fast and reliable. We are very pleased with them. We don’t do incrementals, we do a full backup. We do a ‘save while active’ so we can continue producing for all but about 15 minutes of the time. We have not had one problem with the 3590’s since they were installed two months ago."
Trends in storage are based on the increasing need for faster, cheaper media. Most organizations choose a combination of storage media depending on the application and retrieval time needed. An HSM plan can include having DASD for immediate storage, and then optical for intermediate backup and document storage, with archival and disaster storage on tape. Storage vendors are working to extend the capabilities of each type of storage, creating an overlap for storage applications. For example, optical seems best suited for document storage, but tape can also be used.
In an effort to increase market share, vendors continue to improve both the process of and media for storage. DASD capacity has grown from 4 GB to 9 GB to 18 GB, resulting in lower costs. Compression technologies in both DASD and tape, while slower in processing, allow for even greater storage capacity. Optical vendors are now marketing audio and video capabilities in conjunction with data and document storage.
Each storage method has its own niche. Tape is still the preferred storage for disaster recovery, DASD continues to increase for immediate storage, and optical storage is finding greater use as a legal and historical means for document storage. The challenge will be to make the methods compatible as part of a HSM.
It is essential for companies to develop HSM plans that meet the immediate, short term, and archive storage needs of the organization. Part of the plan should include data already in storage (many organizations still have 8mm tape) and for transferring data between levels of storage. For example, Popular Club Plan uses DASD to mirror and incrementally journal transactions (every 2-3 hours) as its immediate and short term storage plan, with a daily tape backup taken off site.
Foote Memorial Hospital has a similar plan. Foote uses a second AS/400 to mirror the primary AS/400, and as a backup. Foote also backs up daily on tape taken off site, but it maintains a need for ready access to recent patient records. To rely on paper records takes too much time and space, so Foote creates visual documents that are stored on optical disks. The optical disks are stored in a local juke box and later removed and taken off site for storage. This process meets both the practical need for access to the patient information as well as the legal requirement to keep a clear record of a patient’s treatment. "Once we have all our inpatient information scanned, the optical version will be our legal medical record. That will be our archival record."
Storage is a dynamic process characterized by change and increased performance, so your storage plan should address future concerns as well as today’s needs. Establish storage parameters. Use historical daily business data to help create a plan for rapid retrieval storage, local storage, and archival storage. Whether you develop a sophisticated, software based HSM plan or an ad hoc, written-on-a-calendar one, you need a plan. Without a storage plan you may find yourself buried by a data avalanche.