Tape's new love affair with disk


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Alternative disk and tape systems

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Not all users can afford a high end, tightly integrated disk and tape system. If budget dollars are scarce, consider these alternatives:

Copan Systems Revolution 200T: The Revolution 200T offers up to 896 drives and 224TB of capacity in a single cabinet. Using its Massive Array of Independent Disks (MAID) technology, it powers on and spins up disk when needed, limiting wear and tear on SATA drives. The Revolution 200T emulates multiple tape libraries and tape drives (LTO, DLT, SDLT and 9840), and can present 56 virtual tape libraries or drives when fully configured.
FalconStor's Virtual Tape Library: This software product runs on an off-the-shelf Intel-based Linux server, connects to any SAN or direct-attached Fibre Channel, SCSI or SATA disks and presents the disk as virtual tape drives/libraries. It can emulate a variety of tape drives (SAIT, SDLT or LTO) and libraries (ADIC, HP, IBM, Sony, StorageTek), and works with most backup software packages. It can be used in conjunction with existing tape libraries to export the virtual tape drives/libraries to physical tape cartridges.
Overland Storage REO 4000: This box offers up to 8TB native capacity in a 2U form factor with Gigabit Ethernet iSCSI and optional Fibre Channel connectivity. The virtualization software on this device allows the unit to present its disk as either disk or tape images or a combination of both. The disk may be configured as JBOD, RAID 0 or RAID 5, and the unit supports up to a total of 16 LUNs or virtual tape drives. Pricing starts at around $12,500 for a 2TB system. Overland also offers a smaller unit, the REO 1000, with a MSRP of $5,000.
Spectra Logic's Spectra RXT: This is a portable RAID Serial ATA disk pack. Depending on how it's configured, it can operate either as a standalone solution or it can be inserted and managed in a standard Spectra T950 tape library drive and media bay. Each RXT can hold up to 400GB of SATA disk and offers RAID levels 0, 1 and 5. The RXT emulates LTO-2 tape drives and can be used with most backup software packages.
If you can't beat 'em, join 'em. That's the rallying call embraced by tape library vendors as they respond to the steady encroachment of disk on their core tape business. Front-end software transforms disk into virtual tape drives and policy-driven backup software handles the data migrations from the disk to the tape and back again. This new climate of coexistence between disk and tape gives users a powerful new tool for improved data protection, high availability and information lifecycle management (ILM). There are two compelling reasons to deploy disk in front of tape libraries: better backup and recovery times and lower costs.

Jumping on the cheaper disk bandwagon, tape library vendors now provide their own ATA disk arrays with front-end I/O controllers running tape virtualization engines that present themselves as virtual tape drives to backup software. The new virtual disk interface gives storage administrators the ability to transparently choose between tape and disk as the primary backup target and to migrate data between the two using policies nestled within their backup software. The integration of disk and tape also frees users to replicate data during off-peak times to off-site disk arrays for disaster recovery purposes, and then transfer the data to tape to satisfy vaulting requirements.

Despite the appealing benefits that closely integrated disk and tape offer, users first need to verify that the vendor's disk array tape virtualization product is compatible with their backup software and storage environment. For example, Spectra Logic Corp.'s disk-based RXT appliance only emulates LTO-2 tape drives, while IBM Corp.'s B20 Virtual Tape Server (VTS) systems only provide a 3490 tape drive target. The limited tape selection could be a compatibility issue in shops where either SDLT or SAIT are the main tape media used. For vendors targeting Unix and Windows environments, the trend increasingly is to support LTO as the standard virtual interface.

IBM/Tivoli targets its disk/tape product for storage environments with mainframe, Unix and Windows operating systems. IBM offers its disk-based B series line of VTS, along with its 3590 tape systems. The VTS and 3590 tape systems can be monitored and configured using Tivoli's Storage Resource Manager (SRM) and Storage Manager (SM) tools, which enable policy-driven data management to move data between the virtual and real tape subsystems.

Storage Technology Corp. (StorageTek) also offers a range of tape libraries and disk subsystems for MVS (mainframe) storage environments. StorageTek's L, SL, PowderHorn and TimberWolf tape libraries work in conjunction with its B, D and V series of disks under the umbrella of the company's Virtual Storage Manager (VSM) software. The VSM software emulates T9840 and T9940 tape drives. In addition to the VSM software, StorageTek also offers Storability Software Inc.'s Global Storage Manager (GSM) that reports on both the tape libraries and disk arrays.

Recently, a number of storage vendors have partnered to fill gaps in their disk/tape offerings. Advanced Digital Information Corp. (ADIC), for example, filled two holes in its product lineup through its recent alliance with EMC Corp. ADIC offers neither disk arrays that compete in the high-end and midrange areas of the market nor storage resource management software that works outside of their product line. EMC fills these gaps with its high-end and midrange arrays and its Control Center SRM software. EMC also provides an enterprise tape library product to round out its ILM strategy.

This was first published in September 2004

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