Generally we face lot of challenges during the configuration of Tape devices for use by Networker Server and storage nodes, thus resulting in spending more time during troubleshooting. Most of the time, problems would have been avoided had we followed the best practices. The following technical note describes SAN best practices on how to configure tape devices for use by NetWorker server and storage nodes.
The following are recommendations for best practices in SAN environments including Clariion family of products:
- Use separate zoning for tape devices. Zones should not mix disk and tape devices.
- Use single initiator zoning. Each SAN zone should contain only one HBA, but it can contain number of targets (tape devices).
- Avoid using 1Gbit interfaces. Fiber channel protocol used for 1Gbit interfaces (FCP-1) is not tape-safe.
- Avoid using multi-vendor switches in a single SAN cloud. Combining switching equipment from different vendors causes equipment to run in compatibility mode which does not include FCP-2 tape safe extensions.
- Use dedicated HBAs for tape devices due to inherent differences in data streams (short blocks .vs. sequential).
- Limit zoning of tape devices to only systems which will actively use them. Limiting the size of each zone reduces chances of external interferences and allows for quicker diagnostics in case of any issues.
- When planning new environments or expanding existing ones, take into account all parts of the data path to avoid bottlenecks. For example, zoning multiple high-speed devices to a single HBA which cannot sustain such data transfer is not recommended. Also, having multiple high-speed HBAs in a single system and connected on the same bus will result in a bottleneck inside the system bus itself.
- Avoid over-subscription of inter-switch links, which can lead to I/O delays and potential timeouts. When applicable, enable congestion control on fibre channel.
- When performing SAN zoning changes, avoid changes for zones in which the devices are active (performing backup or restore). Changing zones while data transfer is active can interrupt the data transfer, thus causing the backup or restore operation to fail.
For more information on configuring the tape devices, please refer to the attached technical note " Configuring Tape Devices for EMC NetWorker" or search the same in powerlink for latest document.