Mainframes are able to work with and process data using many different operating systems, applications, and protocols. They are also able to save that data onto many different kinds of storage media. What follows is a brief overview of some of the most common types of mainframe storage media.
One of the earliest forms of storage media for the mainframe is magnetic tape. This method involves saving data to magnetic tape through a process of digital recording. Most modern magnetic tape storage is packaged in cartridges that can be removed from the tape drives and moved into storage for long-term data archives. The tape drives are the hardware used to write the data to the magnetic tape. Magnetic tape storage is nearly obsolete for handing active data since the time it takes to back up and restore data from magnetic tape cartridges is not competitive with other storage media. However, it is a cost-effective way to backup large volumes of inactive data. Data retention regulations and other legal obligations to keep copies of data for longer periods of time make this method practical for long-term archives. Data stored on magnetic tape should be encrypted even if it is no longer of value to the business and is only being retained for regulatory purposes.
Disk storage is the most common storage medium for modern computers, including mainframes. Basic disk storage options include types like serial ATA, Fiber Channel, SCSI attached storage, and even solid-state storage devices. These types of storage offer a spectrum of options to find the right balance between storage capacity and speed of reading and writing data. The data that is actively accessed and processed on the mainframe’s disk storage media should be regularly backed up and archived so that it can be quickly recovered in case of hardware failure or data corruption. Disks get corrupted and data can be lost if there is not a recent backup, and preferably multiple backups. Having an on-premise backup provides for quick recovery, but keeping an off-site backup makes it possible to recover from having the main system go down.
Virtual Disk / Virtual Tape Storage
A third option is virtual storage, either through virtual tape or virtual disk. Virtual tape and virtual disk storage provide high-capacity and relatively inexpensive disk storage by making multiple attached storage devices emulate tape volumes or one larger disk storage volume. The data recovery tools can then see this virtual storage volume as a single unit, even if it is actually spread across an array of hardware. Virtualizing the storage makes it easier to integrate with existing backup software, processes, and policies. It also makes it easier for administrators to replicate the virtual disks and duplicate them across multiple copies of backups.
The disk and virtual disk storage media are forms of mainframe DASD (direct-access storage device), which are any secondary storage devices that can connect to the mainframe. The direct-access part of DASD mean that the data stored on these devices can be accessed without having to fast-forward through the data, like you have to on tape storage.
Although this makes DASD much more efficient at finding stored data, over time as the DASD is written to and re-written to, the disks can become fragmented. ASPG’s DASD management product, InfoDASD, helps control storage costs through data collection, reformatting and reporting for DASD subsystems as well as providing the tools to plan for future storage needs. To learn more about InfoDASD, download the product guide or try it out yourself, by requesting a 30-day free trial.