management: Who Still Makes Mainframe Disk?
A couple of days ago, I asked a z/OS systems programmer friend to name the vendors manufacturing disk (or DASD) subsystems for the mainframe - specifically z/OS. He came up with two: IBM and EMC. But there are more than two vendors today who offer mainframe disk. So exactly who sells mainframe disks today?
A Google search for 'mainframe disk' quickly shows IBMs page with their disk storage for z Systems mainframes. For DASD subsystems, this is the DS8880 series: DS8884, DS8886 and DS8888 (from smallest to largest). In May of this year, IBM announced new 1.8TB 10K and 6TB 7.2k rpm disk drives to further increase the capacity of these subsystems. An all-flash DS8888 subsystem was also announced at the same time.
In February of this year, EMC also announced an all-flash disk option for its mainframe VMAX subsystem. This complements the 2014 release of the latest VMAX3 disk subsystem, with a new architecture and internal operating system. This new subsystem was advertised as performing three times faster than the previous VMAX subsystem, with 50% lower total cost of ownership, and greater than six-nines (99.9999%) availability.
In 2014, HDS matched EMC, announcing their VSP G1000 enterprise disk subsystem. This announcement advertised the VSP G1000 as 'the most reliable hardware on the planet.' HDS have also been a mainframe disk manufacturer for decades, and this new subsystem was also advertised as three times faster than the previous VSP subsystem.
HP Enterprise wasn't left behind in 2014, announced their XP7 disk subsystem at the same time as the HDS VSP G1000. This is no coincidence, as the XP7 uses VSP G1000 hardware. There is some discussion as to whether the XP7 is a rebadged VSP G1000, or if HP have added enough features to make this their own. However HP Enterprise have been using HDS disk hardware for their own mainframe-capable disk subsystems for years.
An interesting new arrival is Israel-based Infinidat. Although not yet announced, media reports have indicated that a mainframe-capable InfiniBox disk subsystem isn't far away.
What's the Difference?
Infinidat aside, the above mainframe DASD is similar in most areas. It is all based on similar RAID-based architecture with all the normal cache, connectivity and other mainframe DASD features. All are general subsystem that can be used by UNIX/Microsoft Windows based servers, with mainframe-specific features. They also all offer normal DASD features including:
Vendors will also discuss relative advantages in performance and footprint. For example, EMC claimed in February 2016 that its VMAX3 system used 40% less floor space, 23% less cooling and 21% less power than its leading competitor. And of course, there's the all-important pricing.
- XRC - continuously updated remote copy using the z/OS data mover in DFSMS.
- PPRC - continuously updated remote copy without relying on z/OS. Different vendors have different names (TrueCopy for HDS, SRDF for EMC) and implementations of PPRC, but the functionality is pretty much the same.
- Flashcopy - the ability to immediately create a copy of a dataset or entire volume. Usually an optionally priced feature. Called TimeFinder by EMC, and Snapshot by HDS.
- zHPF - support for IBMs high performance FICON for improved channel speeds.
- PAV and HyperPAV - support for IBM Parallel Access Volumes to reduce wait times queueing for a path to a disk unit.
- Hybrid and all Solid State Disk (SSD) options.
- z/OS Discovery and Auto Configuration (zDAC) support - automatic discovery of DASD.
- Tools and utilities to manage the disk subsystem.
- Various disk tiering options, so more frequently accessed data resides on SSD or faster disk devices within a subsystem. All support DFSMS features to supplement this disk tiering.
- Automatic subsystem-based back-end encryption - encrypt data on physical disks.
But there are occasionally some interesting things that separate these vendors. For example, EMC has recently announced Data Protector for System z (zDP) for its VMAX3 and VMAX All Flash disk subsystems. zDP is a z/OS application that works with the VMAX hardware to automatically take snapshots of data at intervals as small as 10 minutes, and retain each copy. So a dataset that has been corrupted can be quickly restored from one of these snapshots.