Improving disaster recovery with Virtual Tape Libraries in Mainframe Environments

By Deni Connor

Principal Analyst, Storage Strategies NOW

Recovering from disasters is an arduous process for mainframe data center managers who rely on tape-based backup jobs – it’s a process often fraught with the fallibility of tape — media errors, time-consuming tape mounting, security risks caused by data loss and the timely and costly retrieval of data from off-site locations. Companies’ recovery time objectives (RTO) and recovery point objectives (RPO) must synch with the technology they use for protecting their mainframe data and with how they manage their off-site disaster recovery (DR) and business continuity operations.

Usage of virtual tape libraries (VTLs) such as the Bus-Tech Mainframe Data Library (MDL), which emulate tape operations but on disk, eliminates these concerns. VTL disk-based technology makes back up operations faster and recovery even faster than tape – in the process of backing up data and recovering it, VTLs generally improve an organization’s disaster recovery operations and their RTO and RPO

Typical Backup and Disaster Recovery Scenario

Traditionally, customers with mainframe tape-based data protection and DR schemes have relied on backing up data to IBM 3480/3490/3590 tape drives or another form of tape drive unit. The process of backing up data to tape is time consuming and often compromised by too short and untenable backup windows, media errors and the prospect of data loss in the process of shuttling tapes to an offsite facility.

In a typical backup operation, a mainframe shop backs up their data nightly. In the morning, a truck arrives to transport the tapes off-site. The contractor who picks up the tapes has service level agreements (SLAs) with the customer that stipulate that the tapes will be catalogued and made available 24 hours after they have been picked up.

Timely recovery is another matter, If a disaster should occur that leaves the site unavailable, the following occurs: Rather than returning the tapes to the original site, the contractor will deliver the tapes to the DR site – optimally, within 48 hours of notification. Data center managers, challenged to meet recovery time objectives, are stuck retrieving data that is not in cache and thus causing tape drive contention, and having to perform numerous mounts and seeks to find the data that needs to be recovered. That is, if the data on this tape is even recoverable.

Time to recover data can be significant – amounting to not just hours, but days to recover the most business-critical data or weeks for data that is deemed to be less important to the business.

 

 

Why Virtual Tape Libraries

Virtual tape libraries (VTLs), which emulate tape-based operations and appear as a collection of tape drives to the mainframe, are being used more often in data centers, where they save space occupied by dozens to hundreds of tape drives and thousands of tape cartridges.  Without requiring any library management or allocation changes, VTLs eliminate tape from the data center and by doing so dispense with the problems caused by media errors, lost tapes and the time delay of recovering data when a business needs it. They eliminate the problems of allocating tape cartridges, media mounting, tape positioning and media eject operations.

VTL’s disk-based technology means that time-consuming tape mounts, the procuring and loading of scratch tapes, and backup tape logistics and off-site shipments can be eliminated. Backups and recoveries that formerly took multiple volumes and multiple mounts, can take place almost instantaneously from the disk attached to the VTL – almost according to one source, as fast as retrieving data from DASD.  VTLs, because they are disk-based, also eliminate streaming problems that affect the efficiency of tape drives and reduce data transfer speeds. Irrespective of the amount of data being streamed, VTLs back up data at the speed of the disk.

In addition, many VTLs have the ability to replicate or vault data over IP to offsite locations for disaster recovery and business continuity, thus speeding disaster recovery.  This capability is a significant time saver over lengthy tape recovery operations where tapes must be transported to the disaster recovery site before recovery can occur, searching for the correct set of tapes to recover and the time spent mounting tapes and reading serially through the data. Replication of data that is encrypted over the WAN also eliminates the risk of tape theft or loss.  Failing back to the original site after the disaster is also much faster with VTLs – changes made to the data simply needs to be replicated back for operations to resume normally.

And, by increasing backup performance and recoverability, VTLs allow organizations to complete backup and disaster recovery operations within prohibitive backup windows and meet service level agreements for business-critical applications.

 

The Bus-Tech Mainframe Data Libraries

Bus-Tech’s Mainframe Data Library (MDL) is a family of virtual tape controller or ‘tape-on-disk’ system for IBM mainframes that optimizes tape-based mainframe operations by emulating them onto low-cost, permanently mounted, open systems network-attached storage (NAS) or Fibre Channel (SAN) disk.  It allows IBM 3480/90 and 3590 tape functions to be emulated and supports as many as 1,536 emulated tape drives.

The Bus-Tech Mainframe Data Library (MDL) replaces Automatic Tape Libraries (ATL) and Virtual Tape Servers (VTS) with an open systems-based, low cost storage alternative that replaces tape. It attaches to the IBM zSeries or compatible mainframe via FICON or ESCON connections and looks to the z/OS, OS/390, VSE or VM operating systems as standard IBM tape drives.

The MDL appears to the mainframe as a collection of tape drives that can be configured into multiple ATLs; similar to an  IBM 3494 Virtual Tape Server, although it operates differently. The VTS is a tape-based system that uses disk as a cache for data being written to or read from a tape. The MDL is a disk-based system that doesn’t use any tape. In emulating tape drive activities, the MDL preserves each tape volumes’ identity with its Volume Serial Number (VOLSER).

The MDL is available in four models, each for a different market segment ranging from small and mid-size enterprises to the largest data centers. Depending on which model the MDL has from one to twelve 4Gbit/sec. FICON adapters or two to twelve 17Mbit/sec. ESCON channels for mainframe attachment and 4Gbit/sec.,  dual ported Fibre Channel HBAs or dual ported 10/100/1000Mbit/sec. Ethernet network connections. Alternate mainframe paths span as many as 64 logical partitions (LPARS).

The four models of the MDL are the MDL-1000, MDL-2000, MDL-4000 and the MDL-6000. The MDL1000 and 2000 are standalone units that fit into a standard 19” rack. The larger MDL-4000 and MDL-6000 are housed in a stand alone cabinet made up of independent emulation nodes with self-contained network gear such as switches, power distribution units, etc. The high-end MDL-6000 can emulate as many as 1,536 IBM 3480/3490 or 3590 tape drives.  These models can be used in any combination to allow them to be tailored to the specific needs being addressed.

Figure 1. The Bus-Tech Mainframe Data Libraries from the MDL-6000 to the MDL-1000 are suited to the needs of large enterprises to small and mid-sized businesses.

Model	# Channels	# Tape Drives Emulated	Performance
MDL-6000	6 to 12 FICON	768 to 1,536	1.2GB/sec.
MDL-4000	4 to 8 FICON or 2 to 12 ESCON	512 to 1,024	800GB/sec.
MDL-2000	2 FICON or 2 to 3 ESCON	256	200MB/sec.
MDL-1000	1 FICON	256	100MB/sec.

The MDL-2000 has two 4Gbit/sec. FICON or  three 17Mbit/sec. ESCON channels for mainframe attachment. Alternate mainframe paths span as many as 64 logical partitions (LPARS). It also connects to the open systems network with either dual ported 4Gbit/sec. Fibre Channel or dual-ported 10/100/1000Mbit/sec. Ethernet connections.

The MDL Series of virtual tape libraries also improve on reliability over tape by using error-correcting RAID disks.

Further, each MDL works with IBM z/OS, OS/390 v2.4(+), VSE, VM/ESA, TPF and z/VM mainframe operating systems, as well as Unisys OS2200.  It supports IBM’s Object Access Method (OAM) and the Unit Information Model and is compliant with IBM System Managed Storage (SMS). According to Bus-Tech, the MDL competes with IBM’s TS7700 and the Sun StorageTek VSM. In addition, Bus-Tech’s MDLs work with many vendors open system storage including EMC, HDS, IBM, Sun and Compellent.

SSG-NOW Assessment

With over 300 VTL controllers in 17 countries installed, Bus-Tech leads the way in mainframe tape replacement and disaster recovery assurance.  The company’s Mainframe Data Library, first introduced in 2002, uses RAID protection, encryption and IP replication to eliminate the risks associated with tape media and allows the detection and repair of media errors. In addition, with Bus-Tech’s MDL, no channel extension hardware is necessary as the MDL can bi-directionally replicate data over the WAN using the IP network. Further the company’s ability to automatically resynchronize communications in the event of a WAN outage and its ability to test DR replication are a boon to the product. The MDL’s use of IP for data vaulting means that customers can dispense with expensive and proprietary communications links and offsite transportation of tapes.

VTLs such as Bus-Tech’s Mainframe Data Library can reduce or eliminate manual tape handling, the transport of physical media and almost any consequence of data loss. With VTLs and their replication capability, recoveries can be handled much faster that with tape-based operations, thus improving an organization’s RTO and RPO. They provide a single point of control for offsite data, while leveraging existing staff competency.

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