Virtual Tape Library (VTL)

What is a Virtual Tape Library ? An Introduction

Tape technology remains the most cost effective backup solution till date. With current tape technology, tape media have a lifetime of 30 years or more and therefor are the number one choice for data archival. In recent years disk based backup gained popularity due to a drop in disk prices and due a lesser need for manual intervention. The performance of disk based backup is generally consider faster and individual file restores from disk are significantly faster due to faster seek times.

A virtual tape library (VTL) is a disk based backup system which appears to the backup host as a real tape library system. Backup streams are however written to and restored from disk. The biggest advantage of a VTL over other disk based backup solutions is its seamless integration into an existing tape backup infrastructure. Backup applications, policies, licenses etc need not change due to a VTL emulating an existing tape library system.

Benefits of a Virtual Tape Library (VTL) system

Improved backup and restore times

Disk based backup offers faster backup and restore times. Sequential access of data is still maintained by VTL system by writing the backup data to disk in a sequential manner. When compared to other disk-to-disk backup (D2D) solutions, virtual tape libraries are high performance solutions with access to the virtual devices over the storage area network (SAN) while a D2D system utilizes a NAS network. QUADStor VTL devices can be accessed over iSCSI, Fiber Channel (FC) and an InfiniBand network.

Reduced tape media handling

Handling of tape media is greatly reduced, hence lesser manual intervention is required. Only data needed for archival purposes would have to be transferred to a physical tape, reducing the amount of tape media that is eventually needed.

Easy integration and Interoperability

Tape libraries and drives from leading manufacturers are emulated. From a backup application’s point of view nothing needs to change, and to it there isn’t a difference between a virtual tape and a physical tape library. The integration of the VTL solution into the backup environment is seamless and non‐disruptive.

Multiple VTL instances

Multiple VTL instances can be created and one or more VTL instances can be dedicated to a host. Each backup server would direct its backups to its own VTL instance, removing the need for tape library sharing and backup stream multiplexing. Also multiple simultaneous backup streams improve overall backup throughput.

Dynamic disk allocation

Storage is allocated to a virtual cartridges on demand removing the need for pre allocation of disk space. Additional disk storage can be configured at a later point of time to increase the available storage capacity. Additionally disk storage can be categorized into storage pools and virtual cartridges can be associated with a storage pool. For example a WORM pool can be created for virtual cartridges with WORM property enabled.

Data deduplication

The VTL extended edition supports inline data deduplication with support for backup data streams from leading backup applications. With data deduplication, store terabytes of backup data for a fraction of the storage cost.

Data compression

Data compression decreases disk capacity requirements with translates to lesser storage costs. Data can be compressed prior to storing on disk, the compression algorithm used is fast and can achieve 2:1 compression ratios.

Disaster Recovery

With the VTL extended edition replication virtual tape data to one or more remote VTL servers for disaster recovery. Auto replication to a remote server is supported for automatic disaster recovery management

Tape Import/Export

Data from a virtual tape can be easily exported to a physical tape either manually or can be triggered by backup application. Storage pool thresholds enable retention of exported virtual tape data for certain periods of time (tape caching)

QUADStor's Virtual Tape Library

QUADStor Virtual Tape Library software is a high performance VTL solution emulating tape libraries and drives from leading hardware vendors.


  • Fiber Channel (FC), iSCSI, InfiniBand and local SCSI access
  • Dynamic storage allocation
  • Data deduplication (Extended Edition Only)
  • VTL replication (Extended Edition Only)
  • T10 logical block protection (Extended Edition Only)
  • Physical tape import/export (Extended Edition Only)
  • Easy storage management with storage pools
  • Simple and intuitive browser based management


QUADStor VTL can be setup in a matter of few minutes.
Documentation can be accessed from

Product support


Technical Specifications

Operating System RHEL/CentOS 6.x, 7.x, Debian 7.x, 8.x, SLES 12, FreeBSD 10.3
Number of Virtual Tape Libraries Up to 128 VTLs or standalone virtual drives per system
Number of Virtual Cartridges Up to 60000 virtual cartridges per system
Host Connectivity iSCSI, Fiber Channel (FC), InfiniBand and local SCSI access

Tape Library Emulation

Vendor Library Emulation
ADIC Scalar 24
  Scalar 50
  Scalar 100
  Scalar i40/80 Series
  Scalar i500
  Scalar i2000
  Scalar i6000
Quantum/ATL M1500
  PX500 Series
HP ESL9000
  ESL E-Series
  EML E-Series
  MSL 2024/4048/8096
  MSL 6000
IBM 3583 UltraScalable Library
  3584 / TS3500
Overland Storage Neo 2000/4000/8000 Series
StorageTek L-Series
L20, L40, L80,
L120, L180, L700
SL150, SL500,
SL3000, SL8500
SpectraLogic 2K/TreeFrog

Tape Drive Emulation

Vendor Drive Emulation
HP DLT VS80, VS160
  SDLT 220, 320, 600
  Ultrium 232 (LTO-1)
  Ultrium 448, 460 (LTO-2)
  Ultrium 960 (LTO-3)
  Ultrium 1840 (LTO-4)
  Ultrium 3280 (LTO-5)
  Ultrium 6250 (LTO-6)
IBM 3580 Ultrium 1
  3580 Ultrium 2
  3580 Ultrium 3
  3580 Ultrium 4
  3580 Ultrium 5
  3580 Ultrium 6
Quantum SDLT 220 (SuperDLT I)
  SDLT 320 (SuperDLT II)
  SDLT 600
StorageTek 3580 Ultrium 5
  T9840A, T9840B, T9840C, T9840D
  T9940A, T9940B
  T10000A, T10000B, T10000C

Backup Software

Vendor Version Inline Deduplication Support
ASG Time Navigator 4.5.x Yes (From release 3.0.16, SIDF backup format)
CA ARCServe 15.x, 16.x Yes
CommVault Simpana 9, 10 Yes
EMC NetWorker 7.x, 8.x Yes
Symantec NetBackup 6.x, 7.x Yes
HP Data Protector 7.x, 8.x Yes
Symantec BackupExec 10.x, 11d, 12.5, 2010, 2012 Yes
Data Protection Manager 2010, 2012 Yes
Quest/BakBone Netvault 7.x, 8.x, 9.x, 10.x Yes
IBM Tivoli Storage Manager, Spectrum Protect 5.x, 6.x, 7.x, 8.x Yes
Veeam Backup and Replication 7.x Yes