Maximize resources through tape sharing

Posted on May 01, 1999

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Maximize resources through tape sharing

There are as many approaches as there are vendors taking a stab at this evolving technology.

By Heidi Biggar

Following in the footsteps of their mainframe predecessors, open systems vendors are embracing the concept of shared storage. In the mainframe world, library partitioning provided emerging Unix applications access to large tape silos. Along the same lines, tape sharing at its most basic level (i.e., library partitioning) in the open-systems arena enables multiple distributed backup servers to tap common tape resources to lower total storage costs. At the drive level, tape sharing can translate into significant availability and performance advantages.

"Partitioning is important because it amortizes the cost of the library across the whole system," says Shaun Walsh, ATL`s recently appointed director of product management for SAN and NAS systems. "Dynamic sharing [sharing at the drive level] is important because of its ability to do device failover should a drive fail during a backup operation."

The need to share data is further heightened because of the exponential increase in storage requirements and today`s increasingly distributed computing environments. And, of course, there is the growing popularity of storage area networks (SANs), whose very premise necessitates tape sharing.

"The two big drivers of tape sharing today," says IDC software analyst Philip Mendoza, "are the management of storage in a distributed environment and the management of devices within the SAN. It`s important for these products, in particular the various software solutions, to stake out their markets early in the SAN market because software isn`t easy to replace once you`ve installed it."

But just like the SAN market, technologies that enable tape sharing are immature. Some of these products are described below.

A little history

In the 1980s, StorageTek developed its Automated Cartridge System Library Software (ACSLS) to address the influx of Unix systems into the enterprise. The software resided on dedicated Sparc 5 stations and directed access to silos among hosts running ACSLS client code.

"The idea was that we had client code for ACSLS (ACS API) that would run on mainframes, Unix, AS/400, VMS, etc. People would then integrate the code into their applications so they could share big tape silos," says Dave Glatfelter, senior product marketing manager at StorageTek. By 1995, ACSLS` reach had extended into the backup and recovery market, with some 35 Unix/NT applications reportedly integrating it. StorageTek later built support into ACSLS for its SCSI-based libraries.

"It was the only way you could share a SCSI library," says Glatfelter. "And because we had broad support for the interface, we had a powerful marketing tool for certain environments." While suitable for 600-slot SCSI libraries, ACSLS wasn`t a good fit for smaller library environments because it required a dedicated server and some rather pricey software, notes Glatfelter.

ACSLS` newest implementation--currently called Media Server--addresses the evolving needs of today`s open-systems environments. Media Server integrates the tape management capabilities of Veritas Media Library (VML) with ACSLS` library management functionality. Incidentally, ACSLS and Media Server will be renamed and positioned as two components of a single product: one for high-end silo environments, the other for the open systems space. (Veritas OEMs VML to StorageTek.)

Unlike ACSLS, Media Server does not require a dedicated server and it supports non-StorageTek libraries, including those from ADIC, ATL, Exabyte, and IBM. Also, because Media Server leverages the ACS API, applications that support ACSLS also support Media Server (e.g., Arcserver, ADSM, Alexandria, CommVault, NetBackup, and Networker). Media Server works in various NT and Unix environments, including HP-UX, AIX, and Solaris.

StorageTek will roll out three phases of Media Server in six-month intervals, beginning this summer. Support for Microsoft`s RSM API will be built into a "lite" version due out later this year. A full-blown version, featuring VML`s media management capabilities as well as SAN support, is expected in the first half of next year.

As for sharing at the drive level, Glatfelter says it`s about 18 months away. "We can put tape management and library management underneath the interface, so backup applications don`t have to be changed. It`s the same sequence of calls. When it comes to tape drives, you`ve got a little problem because backup applications have to change how they use the product." Right now, that means minor changes to code, which translates into new software releases. Glatfelter says StorageTek is working with vendors to get them to code to the interface so they can provide drive sharing underneath the applications.

Software compatibility is key

When it comes to data sharing, ATL`s approach is twofold: to ensure compatibility with leading middleware and backup software and to develop an in-house partitioning and dynamic sharing capability that`s both host- and software-independent.

"We have to be compatible with the ISV vendors," says ATL`s Walsh. "However, products like SmartMedia, RSM under NT, and Veritas VML enable you to virtualize devices and, in the case of SmartMedia, to do some dynamic sharing. What they don`t allow you to do is have any host independence or any independence from the software applications. Customers need access to their data regardless of the platform or the application that`s requesting it."

Announced last May, the PL50 Library Hub enables library sharing in some ATL products. Essentially a software-enriched SCSI-to-SCSI bridge, the hub connects up to three Unix or NT servers running any storage management software to a single ATL 7100, 520, or 2640 series library. The hub can be dedicated to one host or it can be shared, or partitioned, among connected servers. But it does not enable drive sharing, since the hosts are hardwired to drives.

For 80% of the market, partitioning is enough, says Walsh. But as you move up the enterprise, the ability to share drives becomes more important, especially in backup situations. The option to dynamically share drives among hosts allows IS managers to make critical tradeoffs like doubling the number of drives dedicated to a server to reduce a backup window or allowing for device failover for improved data availability.

To accomplish this, ATL has added intelligence to its existing hub and embedded it into its P1000 and P3000 PRISM architecture libraries. The libraries use off-the-shelf PCI adapter cards for plug-and-play connectivity and, soon, plug-an-play tape sharing. "By putting the software on PCI adapter cards, we allow users to easily swap and install cards. If dynamic sharing is needed, users purchase that card, swap it in, and off they run," says Walsh.

By separating the data and control path, ATL has also lifted the PL50`s three-host limitation. The new product, which is undergoing certification, will be available later this year.

The hardware approach

Along these same lines, Los Angeles-based TapeLabs this month began shipping TapeServer. TapeServer uses standard components, including motherboards and PCI adapters, and proprietary code to provide drive and library sharing in multi-platform environments (e.g., Unix, NT, Netware, AS/400, Tandem, and Unisys) via Ultra2 SCSI or Fibre Channel links on both sides of the box.

"That`s a distinct advantage," says Allan Ignatin, TapeLabs` chief technology officer. "TCP/IP is present only if the users have it, but only for out-of-band communication and SNMP messaging." Ignatin says there are significant performance and interconnect issues with drive sharing under SCSI or TCP/IP.

TapeServer supports new and, equally important, legacy drives and libraries from manufacturers such as ADIC, ATL, Breece Hill, Exabyte, HP, Overland Data, Qualstar, and StorageTek. "We could even support LTO," adds Ignatin. Tape Labs says it currently has OEM relationships with four of these manufacturers; ATL says it is not one of them.

"Functionally, TapeServer and our product do some of the same things," says ATL`s Walsh. Essentially, it is our PRISM architecture in a box." Despite the similarities between the two products, there is at least one importance difference: TapeServer offers broad drive and library support, while ATL`s approach is limited to its P1000/P3000 libraries.

TapeServer can be connected to an unlimited number of hosts and tape libraries, though at some point the number of connections becomes impractical. "You`ve got to ask yourself, how many times you can divide a library before it becomes impractical," says ATL`s Walsh. The average number of servers per tape drive is currently 3.4, according to Strategic Research of Santa Barbara, CA.

A three-host/eight-device TapeServer configuration runs about $12,950, which includes mirroring and some basic tape-RAID capability.

Strictly software

Over the last six months or so, a multitude of products enabling library and/or drive sharing have emerged from software vendors. But issues of device and platform interoperability, as well as application support, limit their market penetration, especially in heterogeneous SAN architectures.

"Real cross-device, cross-platform interoperability of the applications is immature," says IDC`s Mendoza. "The Unix pieces are more mature than the NT pieces, and the integration of the Unix pieces with the NT pieces still needs some work."

Seagate`s recently re-launched Backup Exec Shared Storage Option, for example, supports NT and Netware, but does not enable you to share devices across NT and Netware. Also, it is specific to Backup Exec. "We want to get to cross-platform, cross-application," says Glen Simon, product manager at Seagate Software, "but to do that we need a dedicated media manager like VML or ACSLS."

Nonetheless, Seagate is targeting its Shared Storage Option to the SAN market, which industry analysts expect to remain homogeneous for several years. Seagate enables simultaneous, or dynamic, sharing of libraries and autoloaders from ADIC, Compaq, Hewlett-Packard, Overland Data, and StorageTek among multiple backup servers.

"All servers have full access to the tape library, media slots, and tape devices," says Simon. "There`s no need for a dedicated server to play traffic cop. Each server independently issues commands to the robotic arm." Seagate tackles the issue of device contention through SCSI Reserve/Release commands, which is defined by the SCSI specification and implemented in firmware in drives. Fibre Channel connectivity is provided through certified bridges from Atto and Crossroads.

The NT version is designed around Seagate`s Advanced Device and Media Management (ADAMM) database. The database, which resides on one of the servers and to which all other servers are pointed, provides a unified view of shared devices and media. A similar capability is available in the Netware version. "Pooling" enables jobs to be load-balanced across devices.

Starter packages, providing support for two hosts and two drives, are available for $4,995. Additional server and tape drive licenses are available for $1,595 and $1,195, respectively.

Coincidentally, with the release of NetBackup 3.2 this month, Veritas announced its own Shared Storage Option for dynamic drive sharing. The option enables drive sharing in heterogeneous Unix and NT environments. Media management and partitioning, long-time features of NetBackup, are included in the basic backup application.

"So, now in addition to hard partitioning, say, an eight-drive StorageTek 9710 among four NT/Unix servers, two drives dedicated to each server, we can create a queue to acquire more jobs." says John Maxwell, director of product management at Veritas. This refers to the ability of a server to turn its drives over to another server once its job is completed. "All you`ve got to do is add up the cost of buying four 9714 libraries and compare it to that of one 9710 and the pay-back is immediate," he says.

To accomplish drive sharing, Veritas elevated its media server technology. Rather than having the customer nominate one of its media servers as the robotics server, or traffic cop, the robotics server now works with a hub or a switch that`s sitting in front of a tape library to control access to the tape drives.

Version 3.2 supports libraries from vendors such as ADIC, ATL, Dell, StorageTek and Sun, and is certified with switches and hubs from Brocade, StorageTek and Crossroads. Pricing is either $995 or $2,994 per tape drive, depending on the type of library.

Noticeably quiet on the tape-sharing front--at least from the standpoint of drive sharing--is Computer Associates. Last month, CA released Virtual Library Option (VLO), which ties into its existing Network Library Option (NLO). Both options are native to ArcServeIT. Neither, however, provides sharing at the drive level.

NLO communicates through the Tape Library Option (TLO) to StorageTek`s ACSLS, which is essentially fooled into believing it owns the library. "It`s a partitioning of the library among ArcServeIt servers," says Ken Delaney, CA`s product manager of storage. The drawback is that it is certified only with STK 9710, 9714, and 9730 libraries in mixed Unix/NT environments. For users who may not support ACSLS or STK libraries, CA offers VLO, which essentially enables users to partition a single library that`s attached to an ArcServeIT server.

On the SAN front, CA offers Enterprise Library Option (ELO) to ArcServeIT. It currently runs on NT and Netware and has been certified by ADIC, Compaq, and Hewlett-Packard. CA bundles ArcServeIT with ELO and TLO.

Instead of integrating tape sharing into its backup application, Legato is doing it via a middleware product called SmartMedia. Based on SGI`s OpenVault software, SmartMedia acts as a gateway to the libraries, drives, and cartridges. "It provides a standard interface for applications and devices to talk to each other," says Vicki Grey, business line manager for enterprise storage management, Legato.

Grey says that because the backup applications no longer have exclusive control over the devices, multiple instances of the same or different applications can share resources, down to the drive level. Actually, the architecture supports sharing down to the cartridge level, but because data is most often streamed to tape in the open systems market--not written in little bits as it is in the mainframe world--it hasn`t made sense for Legato to implement it.

SmartMedia works with Legato`s own NetWorker, and CommVault Systems has licensed the technology to use in its storage management products. To increase its ISV support, Legato will add an ACSL bridge by year-end and an RSM bridge in the first half of 2000.

Another example of a "bridge" solution is Austin, Texas-based Gresham Enterprise Computing`s (formerly Open Microsystems) Enterprise DistribuTape. Enterprise Distribu-Tape enables multiple Tivoli ADSM version 3 servers to share a pool of tape drives and StorageTek libraries over a conventional network or in a SAN environment.

"It is the bridge between ADSM and ACSLS, and it`s the brains that allows the sharing of devices," says John Groves, Gresham Computing`s CEO. As the client, ADSM requests a volume; Enterprise DistribuTape then prioritizes known tape drives and manages and allocates the services of the library and drives, enabling multiple ADSM servers to share the same library and drives.

Gresham Computing plans to broaden the software`s support to include other manufacturers` libraries and backup applications. Groves says there`s nothing about the technology that inherently limits it to StorageTek libraries, but adding support for other backup applications may prove difficult. However, Groves says that if other applications can be made to write to its Library Manager API, they would automatically coexist with ADSM and Enterprise DistribuTape.

Right now, there are about as many approaches to tape sharing as there are SAN initiatives. What will be interesting to see is what effect the IEEE standard, assuming it`s passed, or an industry acquisition (Veritas` impending acquisition of Seagate Software, for example) will have on the market. Stay tuned.

IEEE works toward management standard

This summer, the IEEE Storage System Standards Working Group (SSSWG) will vote on a Media Management System (MMS). MMS, which leverages Silicon Graphic`s OpenVault media management technology, is a proposed distributed, multi-platform standard for managing removable storage, including magnetic tape, optical disk, and CD-ROM.

"The IEEE MMS standards define a model for working with removable media and a number of protocols," says Jack Cole, chair of IEEE SSSWG. "It defines protocols for communication between and the behavior of library and device managers, but not how these managers are implemented." One such implementation is Legato SmartMedia 1.1, which is based on SGI`s OpenVault.

The system is designed to scale to the computing environment, making it possible to implement "lightweight" or "full-blown" implementations. Additionally, the system is media-neutral (i.e., it applies to tape, disk, optical, etc.); application, platform- and OS-independent; language and content neutral; and modular.

The four primary protocols, as defined in the MMS architecture, are:

- The Session Security, Authentication, and Initialization Protocol (SSAIP), to establish identity, authority, and initial communication with the Media Manager.

- The Media Management Protocol (MMP), used by client and administrative applications to allocate, mount, dismount, and de-allocate volumes, and to administer the system.

- The Drive Management Protocol (DMP), which defines the language which the Media Manager and Drive Manager Communicate. The Media Manager issues load and unload commands to the Drive Manager. The Drive Manager reports drive status, errors, usage stats, etc.

- The Library Management Protocol (LMP) defines the language by which the Media Manager and a Library Manager communicate. A Library Manager manages an automated library or a vault. The Media Manager issues commands to the Library Manager to move cartridges. The Library Manager reports status, errors, and current contents and topology of the library to the Media Manager.

The standard, if passed, will be published this fall. For more information, visit www.ssswg.org.

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TapeLabs` Tapeserver connects to any number of heterogenous hosts and tape drives/libraries via Ultra2 SCSI or Fibre Channel links.

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The primary modules within the MMS are the Media Managers, Library Manager, and Drive Managers.


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