SPAYNE.SEP IBM'S NEW 3390 DASD: HOW DO YOU GET THERE FROM HERE? By Sheila Payne Sheila Payne has over 12 years experience in the computer industry with such companies as Raytheon Data Systems, Philips Information Systems, Protype and Computer Consoles, Inc. Her background includes applications analysis and development, marketing support and sales. Since 1987, Ms.Payne has been a free-lance writer with the firm of Mangione, Payne and Associates, Los Angeles. This article discusses Sterling Software's Volume Allocation Manager (VAM) and DMS/OS products. You may already be aware of the many reasons to migrate to IBM's new 3390 DASD from the older 3380 devices: nearly three times the capacity per square foot of floor space, up to a 40 percent improvement in data transfer rates and a 15 percent improvement in average latency. Best of all, the 3390 provides an 18 percent reduction in the cost per megabyte of disk storage. In fact, when you consider the 3390's lower maintenance costs, reduced power requirements and reduced footprint, savings climb to 20 percent. If you are faced with the task of adding DASD capacity -- even though your DASD farm is pushing at the walls of the data center -- or if your users are clamoring for higher performance, you've probably already decided to migrate to 3390s. That was an easy decision. Now you're faced with the real issue: converting from 3380s to 3390s without massive disruption to your users. Don't despair, help is available. Storage management software tools can minimize the impact of migration on your daily operations. This article discusses how two major corporations are taking advantage of these tools to ease the transition. One corporation, a leading retailer, recently centralized its operations to achieve economies of scale. Dave Lawson, a data storage specialist for the retailer, explained, "Instead of each subsidiary running a separate data center, we combined them into one information technology organization, servicing all business units." The new data processing organization has almost 20 3090 600 class systems MVS/ESA and over nine terabytes of DASD. "Since January, we've purchased only 3390s. We will phase out half of the 3380s this year and the remainder next year," Lawson said. The second organization, a large and progressive super-regional bank, decided to convert to 3390s because of limited floor space in the data center. Randy Lebedz, who is responsible for storage management, explained, "Between January 1989 and May of 1990, the bank increased from 165GB to 425GB of DASD, primarily as a result of mergers and data center consolidations. We were bursting at the seams. The 3390s are giving us a tremendous buyback in footprint, so that we don't have to remodel our data center." Migrating Datasets Dynamically Moving datasets from the 3380s to the 3390s is a major undertaking, particularly when large volumes of data are involved. Shops that have a data mover such as IBM's DFHSM can move datasets by backing them up, then restoring them to the new 3390 devices, or they can use DFDSS for disk-to-disk moves. However, these manual procedures are labor-intensive and time- consuming. A much more efficient way to migrate datasets is to move as much data as possible, automatically and transparently, with volume allocation software. Lebedz explained, "A large percentage of datasets are reallocated on a regular basis. In our shop, for example, within a one-week period, I would estimate that 80 percent of our test datasets are reallocated through DELETE/DEFINE operations. With a product like Sterling Software's Volume Allocation Manager (VAM), we can take advantage of its allocation features to migrate these datasets to 3390s through normal, every-day procedures." This is accomplished by replacing 3380 volumes with 3390s in the VAM Storage Group Member that defines DASD pools. "Any new allocations, even those directed to a specific volume by JCL, are intercepted and redirected to the new volumes," Lebedz said. "That makes the migration much easier for everyone involved." Applications programmers don't have to perform massive JCL changes and, in fact, don't even need to be aware that new devices have been installed. Storage managers are relieved of time-consuming moves that otherwise would have to be done manually -- typically on weekends, so that daily operations are not impacted. Volume allocation software greatly improves a site's ability to perform the conversion quickly. Quick turnaround is important when a number of 3380 devices are coming off lease and must be removed in a short period of time. "We're trying to minimize our costs by minimizing the amount of overlap between the time we bring in a 3390 device and the time we remove the 3380 device," Lawson explained. "One of our data centers has to convert 300 3380s in a single month. That's a lot of data to move in a very limited time window. With VAM, we can migrate datasets to the new devices through normal production, without coordinating everything ahead of time with the applications programmers." Lawson expects to move up to 50 percent of the retailer's data dynamically. "We have over nine terabytes of data altogether. If we can move 50 percent without any manual intervention, we'll save a lot of time," he said. Complicated Migration Moving from 3380 single-density devices to 3380 dual- or triple- density models was a relatively problem-free process because even though the model Ks offered more storage capacity per box, there were no major technological differences. The 3390s, on the other hand, employ new track geometry. The 3390 volumes are more dense and have fewer cylinders (2226 cylinders on the 3390 Model 2 as compared to 2655 on the 3380K). As a result of this difference, block size and space allocation become important considerations when migrating data. Datasets that are blocked for 3380 track size can be migrated directly to the 3390 without changing the block size. However, this results in a considerable amount of wasted space on the 3390 -- 70 percent utilization on the 3390, compared to 98 percent utilization if the block size is optimized for the 3390. Unless you change the block size, you'll eliminate one of the major benefits the 3390s -- much higher capacity per square foot of floor space. Volume allocation software products can help in this area as well. These products can do more than just move the datasets to the new devices. They can also dynamically change block sizes to take advantage of the 3390 track geometry and optimize device utilization, without any JCL changes. Sterling Software's VAM, for example, allows users to create a filter that determines block size, based on the type of device on which the dataset will be placed. Lebedz explained, "I set up a FILTLIST so that block sizes are adjusted dynamically. During allocation, VAM determines whether to place the dataset on a 3380 or a 3390. It then passes the dataset through the filter that looks at the device type and assigns the correct block size." Because 3380s and 3390s have different cylinder capacities, space allocation should also be adjusted when moving datasets between devices. For example, a dataset that requires 100 cylinders on a 3380 would require only about 80 cylinders on a 3390. Adjusting space allocations can be accomplished dynamically with a product such as DMS/OS, Sterling Software's data storage management software. The product takes into account both the source and destination device geometry as it migrates datasets through the storage hierarchy. It uses this information to adjust the space allocation when moving data between devices of different geometries. Mixed 3380/3390 Environments Many shops will operate in a mixed 3380 and 3390 environment for a variety of reasons. In some cases, leases on 3380 devices won't expire for some time; in other cases, data centers will keep 3380s for specific applications. Volume allocation software can provide additional assistance to these shops by allowing the storage management staff to establish rules so that the allocation software can "intelligently" decide if a dataset should be moved to a 3390 or be retained on a 3380 device. The decision can be based on such factors as dataset name, size or performance issues. What About the Rest of the Data? By using volume allocation software for dynamic migration, data centers can reduce the time required for conversion. The allocation software will move a large percentage of the data through normal operation. The two corporations discussed in this article reported that 50 and 80 percent of their data, respectively, could be moved dynamically. At some point, however, the staff will have to schedule manual migration of datasets to convert the remainder of the data to the new 3390 devices. Lawson is using IBM's DFDSS to perform this portion of the migration process. The biggest problem he has experienced is in converting multi-volume VSAM datasets. "We've had problems moving these datasets because DFDSS won't move a multi-volume file unless you have all the volumes listed in the catalog. The problem is compounded because some programmers always include an alternate volume, just in case the dataset grows. DFDSS considers any dataset with an alternate volume to be a multi- volume dataset. We'll have to do a lot of research to ensure that we have the jobs set up correctly and that we've included all the VOLSERs," Lawson said. Other data centers are using storage management software from independent software vendors. Lebedz, for example, is using the DMS/OS Volume Configurator component, which enables users to migrate a single dataset, a group of datasets, a volume or a group of volumes directly from one DASD volume to another using a single command format. "I'm looking forward to implementing DMS/OS version 8.1 in the near future," Lebedz said. "That will give us the ability to perform VSAM disk-to-disk migration. We'll be able to go to the new devices without having to do tape mounts. That will result in a big time savings during the migration." Assistance After Conversion Although Lawson said his shop will rely on Sterling Software's VAM during the conversion, a major reason for installing it was to avoid problems after the migration. Lawson was concerned that removing 3380 volumes could cause a number of jobs to fail because volumes specified in JCL would no longer be available. With volume pooling, data centers can avoid this problem because the allocation software intercepts new allocations and, if the specified volume is no longer installed, it directs the dataset to another volume in the pool. "VAM will guarantee that we won't have abends when allocating new datasets because a job can't find a pack that we have removed," Lawson said. "It's a safety valve. We have so much data to move that we can't possibly coordinate everything with all the users ahead of time. We can notify the users after the fact that those volumes no longer exist." Summary The benefits of the new 3390 technology are clear. Many data centers are anxious to install these devices so they can increase DASD capacity without consuming additional floor space. Performance gains are also a consideration. One installation, for example, recently reported that one of their nightly database jobs is running in three hours vs. four hours since moving it to the 3390s. The migration process, however, can be overwhelming when large volumes of data must be moved. To complicate matters, technological differences between 3380s and 3390s require that block sizes and space allocations be changed to take full advantage of the 3390's higher density storage. Lawson believes that, unless they can afford to migrate very slowly, most shops will require some kind of storage management tool to minimize the manual effort. "The real key is system managed storage in general, whether it's a 3390 conversion or something else. We're moving toward an environment where the applications programmer doesn't have to worry about what kind of device he's using," he said. According to Lawson, data centers will find that converting to new storage devices becomes easier as system managed storage becomes more widely used. "In the future, when IBM makes its next hardware announcement, it will be easier to convert because shops will be well into implementing IBM's DFSMS or other system managed storage products. It will be easier to modify parameters, change pools and direct datasets to the new volumes." By using storage management software tools such as Sterling Software's VAM and DMS/OS products, data centers can dramatically reduce the amount of time storage management personnel must spend on the migration. In many cases, particularly in larger shops, the time saved will more than justify the cost of these software tools. At the same time, these products can make the migration transparent to users and minimize disruption to operations. /* 2182 Was this article of value to you? If so, please let us know by circling Reader Service No. 00.