Tape drives in virtualized environments

We have had a few questions recently about tape drives in virtual environments.  Here is a quick look at it.

Most virtualization systems enable the configuration of tape drives inside a guest container, but the use of such configured tape drives has limited support.

For any virtualization system that does not provide dedicated HBA capabilities, the use of tape drives in guest containers is not supported for production environments. Such configurations can be used for testing or evaluation but never to store production backups. The reason is that virtualized or passthrough drivers have high interruption rates, are not suitable for sequential input/output, and can cause a high number of SCSI resets, even in the best cases.

At the moment, this includes all editions of:

The use of tape drives is qualified and considered safe for virtualization systems that enable full isolation of input/output. The physical input/output interface cannot be shared between guests.

At the moment, systems that have required capabilities are:

This technical limitation does not exist for pure backup-to-disk solutions (using an advanced file type device or Data Domain Boost), and support is based on qualification efforts. The EMC Information Protection Software Compatibility Guide provides the current list of supported platforms.

Specific to IBM LPars, we support if VIO use of dedicated HBAs, but not virtualized ones – the danger of data loss due to usage of sequential SCSI protocol is too high.  In non-production environments, tape drives can be configured and used, but no support is given in case of issues.

As it is, no amount of work from the NetWorker side would ensure sufficient reliability of such configurations.  The usage of IBM LPar and virtual HBAs will remain unsupported for production environments.

This position will be re-evaluated when virtualization vendors introduces new functionality in their platforms.

For example, usage of tape drives was not supported on VMware prior to vSphere 4.0 Update 2 which introduces SCSI isolation layer using VMDirectPath I/O.

Thanks,

Allan (Vlado and Nico)